partially touch each other. Stem articulated, round, and without accessory rays. Mouth central in the midst of five scales, which are foliaceous and bordered by a row of tentacular cirrhi; a large tubular orifice a little behind the mouth.

P. Europaus, Pentacrinus Europæus, Thompson. It is now generally admitted that the observations of Mr. J. V. Thompson have proved that this animal is but the young of Comatula. If no other species of Phytocrinus be found, this genus must be cancelled. Poteriocrinites.-A crinoidal animal, with a round column, composed of numerous thin joints, having in their centre a round alimentary canal, and articulating by surfaces striated in radii. Round auxiliary side-arms proceeding at irregular distances from the column. Pelvis formed of five pentagonal plate-like joints, supporting five hexagonal intercostal plate-like joints, and five plate-like scapula, having on one of the intercostals an interscapulary plate interposed. An arm proceeding from each of the scapulæ. Base probably fascicular, and permanently adhering. (Miller.)

The author of this generic character says, "It is with considerable hesitation that I describe these five plates as belonging to the pelvis; the analogy of their lower articulating surfaces seems perhaps rather to indicate their belonging to the first costal series. I have never yet had an opportunity of seeing the connection of these plates with the first column or joint fairly developed, and it seems possible that the true pelvis may be small and almost concealed. This doubt will be done away by the acquisition of more instructive specimens, and my thus stating the case must be considered as resulting from an anxious desire to check errors. It is not unlikely that the real joints forming the pelvis are so much abbreviated as not to be visible externally. Every one acquainted with fossils must be aware how difficult it is to trace always organic details in them correctly, and how many specimens are sometimes necessary to ascertain a single fact." De Blainville observes that this genus does not appear to differ from Apiocrinites, excepting inasmuch as that the stem is not enlarged at its superior part, and that the basilary pieces of the rays are less approximated, and without doubt less immoveable. The details given by Mr. Miller point out a form differing strongly from that of Apiocrinites, and if his data be admitted there can be little doubt of the generic difference which he records.

P. tenuis, Thin, Vase-like, Lily-shaped Animal. A crinoidal animal, with a column formed of numerous round thin joints, surface of articulation radiating and striated. The plate-like joints forming the cup-like body, articulating by minute striæ. One arm proceeding from each scapula, supporting two fingers. It is found in the Mountain Limestone of the Mendip Hills and in the Black Rock, the 14th bed of Dr. Bright's series ('Geol. Trans.,' vol. iv. p. 193), near the river Avon, Bristol, belonging to the same formation. (Miller.)

The other species recorded by Miller is Poteriocrinites crassus, from the Mountain Limestone in Yorkshire, and the Mountain Limestone at Bristol, near the river Avon, bed 1 and 14 of Dr. Bright's paper in 'Trans. of Geol. Soc.,' vol. iv. p. 193, and in the Magnesian beds of the Mountain Limestone, Clevedon Bay, Somersetshire. Miller further states that the specimen mentioned in Dr. Woodward's 'Catalogue of Foreign Fossils' (page 19, 8. 1.) as coming from Syria, is of this species, and that he (Miller) is indebted to the Rev. A. Sedgwick, Woodwardian Professor, Cambridge, for ascertaining this fact, he having kindly furnished Mr. Miller with a drawing made from the original, now in Dr. Woodward's collection, and under his care.

Platycrinites.--A crinoidal animal, with an elliptic or (in one species) pentagonal coluinn, formed of numerous joints, having a few side-arms at irregular distances. Pelvis saucer-shaped, formed of three unequal pieces, from which five large plate-like scapulæ proceed. Base provided with numerous fibres for attachment. Miller, who thus characterises the genus, observes that the want of costa supplied by the large plate-like scapulæ gives the superior part of these animals a pentagonal appearance, and furnishes so conspicuous a character that they are readily distinguished from all other genera.

and at Mitchel-Dean; also occasionally in Transition Limestone of
Dinevawr Park, and Dudley.
Goldfuss names and describes two additional species, namely,
P. depressus and P. ventricosus.

Cyathocrinites.-A crinoidal animal, with a round or pentagonal column, formed of numerous joints, having side-arms proceeding irregularly from it. On the summit adheres a saucer-shaped pelvis of five pieces, on which are placed in successive series five costal plates, five scapulæ, and an intervening plate. From each scapula proceeds one arm, having two hands. Locality, Transition and MountainLimestone strata. (Miller.)

C. planus. A crinoidal animal, with a round column formed of numerous depressed joints, articulating by radiating surfaces, and perforated by an alimentary canal, pentagonal near the pelvis, which becomes round further from it. From each of the scapula, which rest on the summit of the cup formed by the pelvis and costa, proceeds an arm supporting two hands, each being provided with two series of fingers. It is found at Clevedon, in the Magnesian beds of the Mountain Limestone; at Wood-Spring, Black Rock (14th bed of Dr. Bright's series), near Bristol. (Miller.)

Miller observes that a specimen had occurred to him where the columnar joints were alternately smaller and larger, but that he was not aware whether it possessed sufficient character to be considered a variety of the former species. The same author records three other species, and Goldfuss has added three more, namely, C. pinnatus, C. geometricus, and C. pentagonus.

At

Actinocrinites. A crinoidal animal, with a round column composed of numerous joints, and perforated by a round alimentary canal. the summit of the column is placed a pelvis formed of three plates, on which five first costals and one irregular costal adhere, which are succeeded by the second costals and intercostals and the scapula, from whence five arms proceed, forming two hands with several tentaculated fingers. Round side-arms proceed at irregular distances from the column, which terminates at the base in a fascicular bundle or root of fibres.

A. triacontadactylus, Thirty-Fingered, Radiated, Lily-shaped Animal (Miller); Rock-Plant (Beaumont); Nave Encrinite (Parkinson). A crinoidal animal with a round column formed of many joints, on whose summit is placed a pelvis of three plates supporting five hexagonal and one pentagonal costal plate, on which the second costals, intercostals, and scapula in series adhere, the latter sending off five arms, having each two hands provided with three fingers. Column sending off at irregular distances auxiliary side-arms, and terminating at the base in a bundle of fibrous elongations resembling roots. It is found in Mountain Limestone at the villages of Broughton and Stokes in Craven, Yorkshire (Lister, 1674), and in the limestone strata of the Mendip Hills (Beaumont), and the Black Rock near Bristol. (Miller.) (See Figure in col. 531.)

Miller describes another species, A. polydactylus, from the Mountain Limestone of the Mendip Hills and Caldy Island. De Blainville observes that among the five (seven) new species which Goldfuss refers to this genus-namely, A. granulatus, A. tesseracontadactylus, A. cingulatus, A. muricatus, A. nodulosus, A. moniliferus, and A. tesseratus— A. tesseracontadactylus appears to De Blainville to offer a new combination of the pieces of the test, and even perhaps of the ten rays of the root, each division being dichotomous.

Melocrinites (Goldfuss).-Column smooth, perforated by a smooth or quinquelobate canal. Auxiliary arms Pelvis composed of four articulations or pieces. Primary and secondary costals five hexagonal, alternately placed (sibi invicem impositi). Intercostals five, hexagonal. Scapulæ five, hexagonal, placed upon the costals. Interscapulars four, in the region of the mouth five. Arms five. Mouth at the side of the vertex.

M. hieroglyphicus, Goldfuss. Melocrinites with the articulations or pieces of the cup or calyx nodulous. Found in Mountain Limestone. Goldfuss records a second species, namely M. lavis.

Rhodocrinites (Miller).-A crinoidal animal, with a round and sometimes slightly pentagonal column, formed of numerous joints of three pieces supporting five square plates, in the spaces of whose lateral bevelled angles five heptagonal first costals are inserted. From the scapulæ proceeds an arm supporting two hands. (Miller.)

The same author records the following species:-P. rugosus, from the Mountain Limestone at Caldy Island, on the south coast of Wales, and at the Mendip Hills; P. tuberculatus, from the Mountain Limestone strata; P. granulatus, from the Mountain Limestone of the Mendip Hills; P. striatus, from the Black Rock (14th bed of Dr. Bright's series); and P. pentangularis, from the Mountain Limestone of the Mendip Hills, at Weston-super-Mare, Black Rock near Bristol,

NAT. HIST. DIV. VOL. II.

R. verus, True Rose-like Lily-shaped Animal. Locality, upper bed, No. 1, and one of the lower beds, No. 15, of Dr. Bright's series, distinguishing the Mountain Limestone formation along the river Avon, near Bristol, the Mendip Hills, Mitchel-Dean, the Transition Limestone at Dudley. (Miller.)

Goldfuss adds four species, namely, R. gyratus, R. quinquepartitus, R. canaliculatus, and R. echinatus, the last being Encrinus echinatus of Schlotheim.

Eugeniacrinites (Miller).-Superior columnar joint subpentangular, enlarging above, having the five plates of the pelvis adhering to it by a solid anchylosis. Base, column, joints resting on the pelvis, and fingers, unknown. (Miller.)

E. quinquangularis (Miller); Clove Encrinite of Parkinson; Caryophyllus lapideus, Caryophyllite of Knorr. Found in Switzerland, at Mount Randen (Knorr); also in the canton Zurich and Schaffhausen. (Miller.) Goldfuss records the following additional specios, namely

2 A

synonyms of the latter, Kentucky Asterial Fossil (Parkinson), and Encrinites florealis (Schlotheim), as quoted by Miller, and thus proceeds: "This is extremely abundant in many parts of Kentucky, and on the margins of the Mississippi in a few places. Near Huntsville they are very numerous; and on the surface of a fragment of rock, three inches long by two and a quarter inches wide, sent to the Academy by Mr. Hazard of that place, I have enumerated eighteen specimens of this species more or less entire, and two specimens of the preceding (P. pyriformis). On another still smaller piece of rock are twenty-one specimens, all in alto relievo, two of which are of the preceding species. On a third fragment of rock thirty may be counted, and on a fourth upwards of fifty. That these animals were pedunculated and fixed, there cannot be any doubt. We see at the base of the pelvis a small rounded surface, perforated in the centre for the passage of the alimentary canal, and on the outer margin are very short but distinct radii of elevated lines, evidently intended for articulation with the first joint of the column. The column itself is always found in fragments accompanying the body of the animal, but never attached to it. I think it highly probable that the branchial apparatus communicated with the surrounding fluid through the pores of the ambulacra by means of filamentous processes: these may also have performed the office of tentacula in conveying the food to the mouth, which was perhaps provided with an exsertile proboscis; or may we not rather suppose that the animal fed on the minute beings that abounded in the sea-water, and that it obtained them in the manner of Ascidia, by taking them in with the water? The residuum of digestion appears to have been rejected through the mouth."

Mr. G. B. Sowerby observes, that all the specimens received in this country from Kentucky were changed into a sort of chalcedony or chert, a circumstance which has perhaps not only prevented British naturalists from forming a correct judgment of their natural affinities as a family, but appears also to have had the effect of preventing them from recognising the generic resemblance to the species that occur here, which, bearing so much greater a similarity to some of the Echinida, has caused some of our naturalists to class them together: for it is observable, he remarks, that of perhaps twenty specimens of the Kentucky Asterial Fossil that he had examined only one individual showed the sutures that separate what Say calls the "pelvic scapular and interscapular plates or pieces." The examination of the new species however suggested to Mr. Sowerby the probability that part of the three unequal pieces which Say calls the pelvis, may in fact prove to be costals, thus evidencing one more relation to the Crinoidea. Mr. Sowerby records and describes two species, premising that the circumstance of Say's first species, P. globosa, having been brought from England, led Mr. Sowerby at first to suppose that Say might refer to one of those species that had come into Mr. Sowerby's hands. Say's description, however, in Mr. Sowerby's opinion is so incomplete, and the terms he has used are so vague, that Mr. Sowerby had not been able to ascertain the fact, but thinks, nevertheless, that 'Pelvis deep, saucer-shaped, convex,' may serve to distinguish it from both. Mr. Sowerby's two species are Pentremites Derbiensis from Derbyshire (limestone) and P. elliptica from near Preston in Lancashire.

In a paper ('Zool. Journ.,' vol. iv.) Mr. Sowerby changes the name to Pentatrematites, and records three more species, namely P. angulata, P. inflata, and P. oblonga; all from the calamine mines belonging to the Duke of Buccleuch, on the Lancashire side of the Hodder; and in the last volume of the Zoological Journal,' he describes three in addition, namely P. orbicularis, P. acuta, and P. pentangularis; the last he considers to be the Platycrinites pentangularis of Miller, the arms being imaginary in his figure. Goldfuss describes a species from the transition limestone near Dusseldorf.

De Blainville places this genus at the end of the Crinoideans. It appears to be the connecting link between the Crinoidea and the Echinidae, but to have a much stronger relationship to the former than to the latter. Marsupites may be regarded as a connection between the true Crinoideans and the Comatulæ.

The following is a summary of the distribution of this group of animals, by Professor E. Forbes :

"This important tribe had its greatest development during the paleozoic and secondary epochs, diminishing materially towards the close of the latter, and becoming scant and scarce during the tertiary and historical epochs. They commence their existence with the earliest sedimentary deposits, and arrive at their maximum of development before the close of the paleozoic periods. In the Lower Silurian they are fragmentary, but common; in the upper beds of that formation many fine species occur often well-preserved in limestone. Actinocrinus, Cyathocrinus, Dimerocrinus, Rhodocrinus, Eugenocrinus, Taxocrinus, Trochocrinus, and Hypanthocrinus are British Silurian genera. During the Devonian epoch we find the genera Cyathocrinus and Platycrinus, Taxocrinus, and Adelocrinus. The limestones of the carboniferous period abound in Crinoidea. Numerous species of Actinocrinus, Platycrinus, Cyathocrinus, Poteriocrinus occur, with others of the genera Rhodocrinus, Symbathocrinus, Gilbertsocrinus, Taxocrinus, &c. The commencement of the secondary period is marked by abundance of Pentacrini, indicative of a new series of crinoidal forms. At Lyme Regis, where they have been

found in great numbers, they occur associated with fossil wood in such a manner, that there can be little doubt that they lived attached to floating masses of wood, probably in shallows. Higher up among the oolitic strata, we find the curious Apiocrinus (the Pear-Encrinite) which appears to have lived attached to ancient banks of coral. During the cretaceous epoch the free Crinoids begin to appear, and Comatule seem to have been not uncommon. The genus Marsupites is a remarkable form of this group, and disappears before the commencement of the tertiaries. The last of the fossil Pentacrinites appear in eocene strata, but as the genus still lives it is probable that intermediate species will be found. Comatulæ existed during all the tertiary epochs. In Britain however no trace of it has been found in pleistocene strata. The supposed genera of Echinidæ, Ganymeda of Gray, and Glenotremites of Goldfuss, are only the cups of Comatulie. "It may be noted generally respecting Fossil Crinoids-1st., That all the genera of the family Actinocrinidæ (including such as have cups composed of thin and slightly articulated pieces and having much divided arms), as Rhodocrinus, Actinocrinus, Gilbertsocrinus, Melocrinus, Scyphocrinus, Cyathocrinus, Platycrinus, Dimerocrinus, Hypanthocrinus, &c., are confined to palæozoic strata. 2nd. That all the genera of the family Poteriocrinida (composed of such as have their cups made up of large and strong segments, but in general aspect closely resembling the members of the first tribe), as Poteriocrinus, Isocrinus, and Symbathocrinus, are paleozoic. 3rd. That the genera of the family Pentacrinida (characterised by the strongly articulated segments of their cups and head of the column, and by the side-arms of the latter) range from the triassic epoch to our own times, having their maximum during the oolitic epoch. 4th. That the genera of the family Apiocrinide (characterised by the pear-shaped and articulated suminits of the stem and cup, and the naked column), as Apiocrinus, Guettardocrinus, Millericrinus, Encrinus, and Eugenocrinus, are secondary, and for the most part oolitic. Encrinus is a genus not found in British strata, and characteristic of the trias (Muschel-Kalk). It is the well-known Stone-Lily or Lily-Encrinite of collections. The genus Borigeraticrinus of D'Orbigny, of which two species are however from the chalk, is an exception to the above rule, if the remains of a Crinoid, found preserved in the recent blank of the Antilles, be rightly referred to it. 5th. The Free Crinoids, Comatulidæ, appear to have ranged from the oolitic period to the present time; for in the lithographic slates of Bavaria we find several remains of animals closely allied to Comatulæ. This family appears to have attained its greatest development during our own epoch, and as certain living species are known to pass through stages exactly comparable to the adult state of the Stalked Crinoid, we must regard the Comatulida as the most advanced of crinoidal forms." (Johnston, Physical Atlas.)

ENDECA'NDRIA, the ninth class of the Linnæan system of Botany, distinguished by having nine stamens separate from each other. ENDIVE. [CICHORIUM.]

ENDOCARP. [FRUIT.]

ENDOGENITES, the name for certain Fossil Plant-Stems, as E. erosa, from the Tilgate Beds. (Mantell.)

E'NDOGENS. One of the large primary classes into which the Vegetable Kingdom is divided bears this name, in consequence of its new woody matter being constantly developed in the first instance towards the interior of the trunk, only curving outwards in its subsequent course downwards. That palm-trees grow in this way was known so long since as the time of Theophrastus, who distinctly speaks of the differences between endogenous and exogenous wood. But that this peculiarity is also extended to a considerable part of the vegetable kingdom is a modern fact, the discovery of which we owe to the French naturalists Daubenton and Desfontaines. The path being thus opened, the inquiry has subsequently, and more particularly of late years, been much extended, especially by Professor Mohl, in an elaborate essay upon the anatomy of palms.

Mohl is of opinion that the first year's wood of an Exogen is analogous in arrangement to that of an Endogen, the woody bundles of each leaf curving upwards and outwards to the base of the leaf, and downwards and outwards towards the bark, crossing through those which have been previously developed.

The phenomena of growth in a palm-tree may be taken as typical of the endogenous structure. In the beginning the embryo of a palm consists of a cellular basis, in which a certain number of cords of ligneous fibre are arranged circularly (fig. 1), down the radicle, deriving their origin from the plumule. Immediately subsequent to germination, and as soon as the rudimentary leaves of the plumule begin to lengthen, spiral and dotted vessels appear in their tissue in connection with the ligneous cords; the latter increase in quantity as the plant advances in growth, shooting downwards through the cellular tissue, and keeping parallel with the outside of the root. At the same time the cellular tissue increases in diameter to make room for the descending ligneous cords (or woody bundles, as they are also called). At last a young leaf is developed with a considerable number of such cords proceeding from its base downwards, and, as its base passes all round the plumule, consequently passing downwards alike on all sides of the centre that it surrounds. Within this a second leaf gradually unfolds, the cellular tissue increasing horizontally at the saine time; the ligneous cords, however, soon cease to maintain

anything like a parallel direction, but curve outwards as they pass downwards, losing their extremities in the roots, or in the cellular integument on the outside of the first circle of cords (fig. 1); at the same time the second leaf pushes the first leaf a little from the centre towards the circumference of the plane or cone of growth; the consequence of which is that the ligneous cords next the base of the first leaf are drawn a little outwards, and form descending axes which henceforwards are found at first to curve inwards towards the centre of the young stem, and afterwards outwards towards its circumference. In this manner leaf after leaf is developed, the horizontal cellular system enlarging all the time, and every successive leaf, as it forms at the growing point, emitting more woody bundles curving downwards and outwards, and consequently intersecting the older arcs at some place or other; the result of this is that the first formed leaf will have the upper end of the arcs which belong to it longest, and much stretched outwardly, while the youngest will have the arcs the straightest; and the appearance produced in the stem will be that of a confused entanglement of woody bundles in the midst of a quantity of cellular tissue. As the stem extends its cellular tissue longitudinally while this is going on, the woody arcs are consequently in proportion long, and in fact usually appear to the eye as if almost parallel, excepting here and there, where two arcs abruptly intersect each other. As in all cases the greater number of arcs curve outwards as they descend, and eventually break up their ends into a multitude of fine divisions next the circumference, where they form a cortical integument, it will follow that the greater part of the woody matter of the stem will be collected near the circumference, while the centre is kept comparatively open, and will consist chiefly of cellular tissue; and when, as in many palms, the stem has a limited circumference, beyond which it is its specific nature not to distend, the density of the circumference must, it is obvious, be proportionably augmented. It is, however, a mistake to suppose that the great hardness of the circumference of old palm-wood is owing merely to the presence of augmenting matter upon a fixed circumference; this will account but little for the phenomena. We find that the woody bundles next the circumference are larger and harder than they originally were, and consequently we must suppose that they have the power of increasing their own diameter subsequent to their first formation, and that they also act as reservoirs of secretions of a hard and solid nature, after the manner of the heartwood of Exogens.

When the growth of the stem of an Endogen goes on in this regular manner, with no.power of extending horizontally beyond a specifically limited diameter, a stem is formed, the transverse section of which presents the appearance shown in the following cut.

Fig. 1.

There are a number of curved spots crowded together in a confused way, most thick and numerous at the circumference, comparatively small and thinly placed at the centre; and the only regular structure that is observable with the naked eye is that the curves always present their convexity to the circumference.

When there is no limited circumference assigned by nature to an Endogen, then the curved spots, which are sections of the woody arcs, are much more equally arranged, and are less crowded at the circumference. Never is there any distinct column of pith, or medullary rays, or concentric arrangement of the woody arcs; nor does the cortical integument of the surface of endogenous stems assume the character of bark, separating from the wood below it; on the contrary, as the cortical integument consists very much of the finely divided extremities of the woody arcs, they necessarily hold it fast to the wood of which they are themselves prolongations, and the cortical integument can only be stripped off by tearing it away from the whole surface of the wood, from which it does not separate without leaving myriads of little broken threads behind.

This account of the structure of the Endogenous Stem is identical with that given by Dr. Lindley in his 'Vegetable Kingdom.' Schleiden's view of the structure of the stem, as given by Dr. Lindley, is somewhat different. The following passage expounds this view :"In all plants, the woody bundles, whose development always proceeds from the interior to the exterior, are either limited or unlimited in their growth. Commonly every woody bundle

consists of three different physiological parts; firstly, of a tissue of extreme delicacy, capable of rapid development, in which new cells are continually generated, and deposited in various ways, in two different directions, namely, next the circumference in the shape of a peculiar kind of lengthened cellular tissue with very thick walls, the liber, and next the centre in the form of annular, spiral, reticulate, and porous vessels; secondly of woody cells, which are either uniform in appearance or different, and form wood, properly so called. Up to a certain period the development of the vascular system in Monocotyledons and Dicotyledons proceeds on the same plan; but in Monocotyledons (Endogens) the active, thin, solid, delicate, cellular tissue suddenly changes; the partitions of its cells become thicker, their generating power ceases, and when all the surrounding cells are fully developed, they assume a peculiar form, ceasing to convey gum, mucilage, and other kinds of thick formative sap." From this cause all further development of vascular bundles is rendered impossible, and therefore Schleiden calls the woody bundles of such plants 'limited.' In Dicotyledons (Exogens), on the contrary, this tissue retains during the whole lifetime of the plant its vital power of forma tion, continues to develop new cells, and so increases the mass, ceaselessly augmenting both the exterior (liber) and the interior faces (wood), for which reason Schleiden calls such woody bundles 'unlimited.' "This," he continues, "happens according to the climate and nature of the plant either pretty continuously, as in Cactaceae, or by abrupt periodical advances and cessations, as occurs in forest-trees of Europe. In the latter, the stem forms an uninterrupted tissue from the pith to the bark during every period of life, and the bark is never organically separated from the stem; what is considered their natural separation in the spring is only a rent, produced by tearing the delicate tissue already spoken of, which is present even during winter, and constitutes the foundation of new annual zones, although compressed, and filled with gum, starch, and other secretions. In the spring, being expanded and swollen by the new amount of sap, it is deprived of its contents by their solution." (Lindley, Vegetable Kingdom.") Schleiden's account of the structure of the Endogenous or Monoco tyledonous stem, as given in his 'Principles of Scientific Botany,' is as follows:

"The most simple plants of this division have no vascular bundles, as for instance Wolffia. Those nearest allied amongst the Lemnacea first exhibit definite indications of these; in Spirodela we even find them combined with spiral vessels, but distributed in a plane surface as the necessary accompaniment of a flat stalk. Many of the Naiadea, as for instance Naias, Zanichellia, Ruppia, have only a central vascular bundle. In the remainder we meet with the following modifications:

"1. Developed Internodes.-The stalks and stems have always several rings of vascular bundles, which occasionally inclose a pith, where a circle of vascular bundles are connected by a ring of thickened parenchyma. This is often the most external (usually), often a more internal one, as in Pothos. A portion of the vascular bundle passes through the nodes into the leaf, whilst a part rises into the next internode. Small twigs branch off from all the vascular bundles that pass through the nodes, forming a confused plexus in the node, which, for the most part, merges into the axillary bud. The innermost vascular bundles in the nodes supply the lowest leaves, the external bundles the upper ones, as in Grasses, the Canestemmed Palms, and the Commelinacea. There are many groups have not yet been examined. The whole of the vascular bundles in the same internode are simultaneously formed and developed, and the internode itself, when perennial, does not continue to increase in thick. ness, whether the plant becomes branched or not. The primary axes, like the secondary, only grow upwards; in fact they are devoid of a cambium-layer.

that

"2. Undeveloped Internodes.-The stalks (in Pistia obovata for instance), and the stems of Palms, herbaceous Liliacea, bulbs of Allium, Lilium, &c., have a conical terminal bud, sometimes shorter, in accordance with which the vascular bundles run from below and the exterior, upwards and towards the interior, and then from thence upwards and externally, to pass into a leaf. The arc, which is convex towards the interior, is longer or shorter according to the terminal bud; and the vascular bundle likewise passes through a longer or shorter portion of the whole axis, according to the same conditions. In the full-grown stems of the Palms, the vascular bundles connected with the upper leaves do not reach the base of the stem, notwithstanding the length of the arc. In the simplest case the vascular bundles are wholly isolated; they are however more frequently connected by intermediate branches, seldom from within externally, but often laterally with one another. From this cause, as well as from a more or less extended vertical course of the vascular bundles before they form the arc, the external part of the stem is composed of a thicker cylinder of vascular bundles, whilst the inner portion, composed only of arcs, becoming more and more isolated towards the centre, and cellular tissue increasing in quantity in the inverse proportion, appears much looser.

"However simple we may consider the course of the vascular bundles, in the Monocotyledons, in judging of them according to H. Mohl's researches, it is in fact but seldom so; nevertheless H. Mohl's representation affords the simplest and clearest delineation,

and gives the type from which all the analagous structures must be deduced. The separate vascular bundles, especially so far as they form the arc, by no means always run in one and the same vertical plane, their emergence deviating frequently about 50° and more of the circumference of the stem, laterally from the vertical of their starting point, as may be easily observed for instance in Yucca gloriosa. The Xanthorhea Australis appears to me to differ most strikingly from the simple type of the stem. Here the fascicles of the vascular bundles emerging into the leaves, evidently have a threefold origin from three different zones of the stem. Quite in the interior another plexus of vascular bundles appears, the course of which however I could not make out, as the piece in my possession was not sufficiently large for me to have it. Still it appeared to me that the vascular bundles had not quite reached the middle of the stem. It will at least suffice to draw the attention of more favoured observers to this striking structure. Perhaps the history of the development of Aletris fragrans will afford some conclusions on the point. An old stem of about 4.25 Paris inches in diameter consists of two parts; the primary stem about 7 lines in diameter, in which the vascular bundles exhibit the usual arc-like course and an external much more solid zone, gradually formed by the cambium-layer. The vascular bundles passing from within to the leaf-cicatrices permeate this external layer in a perfectly horizontal direction. The external layer becomes however divided again into four zones, which produce the appearance of annual rings when seen in the transverse section. The three external ones are when taken together of about the same thickness as the fourth internal one; they differ in this, that in the external ones the fibres do not ascend vertically but obliquely, consequently in a spiral round the axis, and wind towards the left; in the second, in like manner, but winding towards the right; in the third again, turned towards the left; and finally becoming gradually horizontal in the fourth. I may remark here that whilst the parenchyma is arranged in vertical rows in the primary stem, it appears to be in horizontal rows between the external vascular, in the manner of the medullary rays.

"An essential difference presents itself here, according as the formative layer is limited to the terminal bud, or whether there is a continuous layer in the whole circumference of the stem below the rind, which is there bounded internally by it. The latter occurs in the case of normally branching stems, as for instance in the Dracana, Aloinea, and Aroidea, the former in normally simple stems, as for instance in the Tulipacea and Palms, with undeveloped internodes. Beautiful investigations on this subject may be found accompanied by the carefully selected results of earlier observations in Unger, (see his Bau und Wachsthum des Dikotyledonenstammes,' Petersburg, 1840, page 34). I must finally make mention of the singular stem-formation in the tropical Orchidaceae. A large portion of these, such for instance as are commonly described as having tubers, have not very thick stems (generally branched) with abbreviated internodes. Those branches however which come to blossom produce a peculiar form, which has hitherto been known as tuber (knolle). Either one of the more central internodes of the blossom-bearing branch swells into a disproportionate mass of very varying shape, or all the lower internodes of the branch form a longer or shorter, more or less thick fleshy mass. In both, as for instance in Epidendrum cochleatum, and Bletia Tankervilliæ, the regular course of the vascular Lundles may be distinctly observed, but in the case of the last-named plant (I know not whether the same holds good for all similarly formed) there is a peculiar vascular system intended for the new lateral buds. Little branches pass from the external vascular bundles, and run together in a horizontal direction below the rind from both sides up to the buds. On cutting vertically through one of these stems we find a transversely-severed strikingly-large group of vascular bundles below the rind, corresponding to each internode. It unfortunately happens with the Orchidacea as with the Cacti that it is a matter of difficulty to obtain a sufficient quantity of material to ascertain its anatomy or its history of development."

Grasses are Endogens with hollow stems strengthened by transverse plates at the nodes. This is seen in the bamboo, whose joints are used as cases to hold rolls, or in any of our indigenous species. In this case the deviation from habitual structure is owing to the circumference growing faster than the centre, the consequence of which is the tearing the latter into a fistular passage, except at the nodes, where the arcs of ligneous tissue originating in the leaves cross over from one side of the stem to the other, and by their entanglement and extensibility prevent the possibility of any rupture taking place. That this is so is proved by the fact that the stems of all Grasses are solid, or nearly so, as long as they grow slowly; and that it is when the rapidity of their development is much accelerated that they assume their habitual fistular character. Independently of that circumstance their organisation is quite normal.

Xanthorhaa hastilis has been shown by De Candolle to have an anomalous aspect. When cut through transversely the section exhibits an appearance of medullary rays proceeding with considerable regularity from near the centre to the very circumference. ('Organographie Végétale,' t. 7.) But such horizontal rays are not constructed of muriform cellular tissue like real medullary processes, but are composed of ligneous cords lying across the other woody

tissue: they are in fact the upper ends of the woody arcs pulled from a vertical into a horizontal direction by the growth of the stem and the thrusting of the leaves to which they belong from the centre to the circumference. Such a case throws great light upon the real nature of the more regular forms of endogenous wood.

Other appearances are owing to imperfect development, as in some of the aquatic species of this class. Lemna, for example, has its stem and leaves fused together into a small lenticular cavernous body; and in Zannichellia and others a few tubes of lengthened cellular tissue constitute almost all the axis; but the examination of such cases is comparatively unimportant, and would lead too much into details of subordinate interest.

By far the most striking kind of anomaly in the stem of Endogens is that which occurs in Barbacenia. In an unpublished species of Barbacenia from Rio Janeiro, allied to B. purpurea, the stems appear externally like those of any other rough-barked plant, only that their surface is unusually fibrous and ragged when old, and closely coated by the remains of sheathing leaves when young. Upon examining a transverse section of it the stem is found to consist of a small firm pale central circle, having the ordinary endogenous organisation, and of a large number of smaller and very irregular oval spaces, pressed closely together but having no organic connection; between these are traces of a chaffy ragged kind of tissue which seems as if principally absorbed and destroyed (fig. 2, A). Fig. 2.

A

A vertical section of the thickest part of this stem exhibits, in addition to a pale central endogenous column, woody bundles crossing each other or lying parallel, after the manner of the ordinary ligneous tissue of a palm stem (fig. 2, B), only the bundles do not adhere to each other, and are not embodied as usual in a cellular substance. These bundles may be readily traced to the central column, particularly in the younger branches (fig. 2, C), and are plainly the roots of the stem, of exactly the sanie nature as those aerial roots which serve to stay the stem of a Screw-Pine (Pandanus). When they. reach the earth the woody bundles become more apparently roots, dividing at their points into fine segments, and entirely resembling on a small scale the roots of the palm-tree. The central column is much smaller at the base of the stem than near the upper extremity.

The age of endogenous trees has been little studied. When the circumference of their stem is limited specifically it is obvious that their lives will be limited also; and hence we find the longevity of palms inconsiderable when compared with that of exogenous trees. Two or three hundred years are estimated to form the extreme extent of life in a Date-Palm and in many others. But where, as in Dracaena, the degree to which the stem will grow in diameter is indefinite the age seems, as in Exogens, to be indefinite also; thus a famous DragonTree, Dracana Draco, of Oratava, in Teneriffe, was an object of great antiquity so long ago as A.D. 1402, and is still alive.