Pistilline or Ovarian Nectaries.

As was stated at the outset, honey is far more frequently secreted in connection with the ovary than any other floral organ,-by the disk if the ovary be superior, and by glands at the base of the style if the Ovary be inferior. The difficulty is to select a few of the best examples. In the Nat. Orders, Compositæ, Leguminoseæ, Boragineæ, Serophularineæ, Labiateæ, Umbellifereæ, and others that might be named, honey is secreted by the ovary or its adjacent parts. In the Ericace the purple glands of the disk are the nectaries (Fig. 49), and the honey is sheltered by

secretes the honey which rises in the tube. Another not infrequent form is shown in Campanula rotundifolia (Fig. 32). Here the upper surface of the ovary secretes the honey, which collects in the hollow formed by the overarching bases of the five dilated filaments. The hairs at the edges of the filaments are intended to close the nectary to insects who are not strong enough to insert their proboscis, as the shape of the corolla secures ample protection from rain. Amongst garden flowers the Fuchsia (Fig 33), Evening Primrose (Fig. 55), and Godetia (Fig. 56), have special honey-glands at the base of the style and on the surface of their inferior ovaries. In each

the bell-shaped corolla, or in the open flowers of Calluna by the awned anthers. In the Snapdragon (Fig. 51) access to the ovarian nectary lies between the bases of the two anterior stamens whose elbows form guides to the humble-bees by overarching the corresponding channels in the lower lip. The hairs of the ovary are also studded with drops of moisture and possibly secrete honey as well as the disk. The chief difference between Snapdragon and Foxglove (Fig. 52) is that in the latter flower there are four entrances to the nectary owing to the filaments being more widely separated. In the common garden Phlox (Fig. 53) the lower fleshy part of the ovary

case the honey wells up into the tube, which in the Fuchsia is contracted at the point where the petals are inserted. In the Evening Primrose the extremely long tube prevents the honey being reached by any insects except humble-bees and moths, and it is further protected from creeping insects by the hairiness of the style at a certain part above the nectary. In Godetia the same end is attained by the closing in of the lowest part of the otherwise open tube with thick tufts of hair which press like buttresses against the style. It is interesting to see how determinedly the pistil pushes itself out of the way of the dehiscing stamens, it will have none of

fringe the mouth are hollow, as is the body, linear or slightly tapered, and roughened at intervals with whorls of tubercles. They are filled in the interior with an albuminous, oleaginous substance, and at fixed places this substance swells out into nodules arranged in a spiral line, of which more anon.

If we now make a transverse section across the body, we notice that there is the large central cavity (archenteron or digestive cavity) before-mentioned, and which is surrounded by a double circle of cells. The outer layer is called the ectoderm, the inner the endoderm; that is, outer skin and inner skin. Between the two there is a thin, apparently structureless, supporting membrane, known as the intermediate layer. The cells of the ectoderm are of a curious shape, something like a pear, the large end being external, and the pointed end touching the supporting membrane. But it will be readily understood that intercellular spaces must occur between these pointed ends of the internal portion of the cells. These spaces are filled up by a mass of smaller cells of no particular shape, they being so crowded together that to retain any primary shape would be impossible. The endoderm cells are large, very irregular in shape, and of a granular appearance. One end of each cell touches the intermediate layer, while the other is directly within the archenteron. The outer portion of each cell contains chlorophyll-coated globules thus giving the green colour to the animal, from which is derived its specific name.

The digestion (or indigestion ?) of a Hydra is extremely interesting. The internal portions of the endodermic cells are each provided wilh a long tapering process called a flagellum, and, besides this, in many cases the protoplasm is pushed out into the archenteron, forming what are known as pseudopodia or false feet. Now, when the food is passed by the tentacles into the mouth, and so into the cavity of the body, it comes in contact with a digestive substance secreted by the endoderm. This digests, to a certain extent, the contained food, leaving, however, portions which it is unable to digest. These latter it takes up by means of its pseudopodia, and draws them into the endodermic cells. Here, it seems, they meet with a more powerful digestive juice which completely reduces them to a state of fine division, and from where the nutriment is ultimately diffused throughout the rest of the cells. But while all this is going on the flagella never cease from agitating the food, and distributing it about the archenteron, so that every cell shares in the work; and then afterwards, as before remarked, excrementitious matter seeks exit through the mouth, and, what is more, finds it. Such a method of digestion as is Qutlined above is termed intracellular digestion. Before we go any farther, sections of the tentacles should be made, when it will be seen that their structure is homologous with the body, and of which they are merely outgrowths. But connected with

them are some peculiar organs which we must not omit to notice. Distributed about each tentaculum are what appear under the microscope little warts, and embedded in their substance small bodies of a shape akin to a soda-water bottle. Each one of these minute organs is filled with fluid and is encircled at the neck inside by several barbs directed backwards. Coiled up in the interior is a long delicate filament, and at the top there is another one projecting outwards, stiff, and apparently immovable. These constitute the organs of defence, or, scientifically, nematocysts. The method of capture is this: a small animal comes swimming by, and in so doing accidentally collides with the extended tentacles, thus touching one or more of the stiff hairs just spoken of. Instantly the neck of the vessel is pushed out, and not only one, but numbers transform their tentacula into spiny masses, and thus the roughened surface enables the prey to be grasped firmly while the long thread does its deadly work. The fluid injected by this latter is very poisonous, and of a nature that paralyses the animal undergoing treatment, so that the Hydra may the more easily get it into its mouth, especially if the capture be a large one, for oftentimes it will be found with a worm struggling in its tentacles.

But it is singular to note the animal's instinct of rejecting unsuitable or harmful food. Should a grain of sand or other foreign matter touch any of the numerous short stiff hairs, before-mentioned, which plentifully bestrew the surface of the tentacles, it does not attempt to evert the long deadly filament, for when one of these threads is everted it cannot be drawn back again but drops off.

As before stated, the Hydra can move slowly along on its foot by the emittence of pseudopodia. The ectodermic cells of the pedal disc secrete a clear, tenacious gummy substance, possessed of great adhesive powers. When the animal wishes to move

quickly it progresses after the manner of the common looper caterpillars, e.g., by stretching out its body to the utmost, and fixing itself in advance by its mouth or tentacula, and then loosening its posterior hold. Either a forward or retrograde motion can thus be made.

In a natural state the Hydra can reproduce itself by budding or gemmation. A small tubercle appears on the animal's body, and gradually grows and expands a set of tentacles, and becomes in all respects similar to its parent, except in size. For some time it remains attached, meanwhile growing and feeding. At last its foothold has become so slender that a slight effort frees it from its parent, though it is not unusual for them while still attached to develop others from their own surface. The sexual method of multiplication may only take place during the summer months. At this time the male organs (testes) are found near the mouth, and consist of from eight to twelve rounded prominences. Each one

consists of a sac whose walls are constructed from the ectoderm cells, and whose interior is formed of the interstitial cells which fill up the spaces caused by the tapering off of the ectoderm cells to the supporting lamina. These interstitial cells now constitute germinal ones, and develop into spermatozoa, resembling those of mammalia, except for the tails, which are undulate. They are liberated by the bursting of the apices of the cells.

Near the foot a large projection arises. This is the ovary. At first it consists of many germinal cells, but later on of only one, which is now called the ovum. The spermatozoa reach this latter by the vibratile motion of the tail, and impregnation takes place. Subsequently the ovum is detached from the body, the sac becomes ruptured and the young Hydra escapes.

The most surprising thing connected with the Hydra, however, is the power of reproducing lost parts, and this it was that caused such excitement when Trembley announced his discovery. If the body be cut into two or more parts, provided each severed part contain ectoderm and endoderm cells, the parts will supply their complements. Thus, sever a Hydra into two portions by a transverse cut; the lower will produce a new pair of tentacles, the upper a new foot and archenteron. You may cut it into a hundred pieces, and each part will reproduce the parts necessary to form a complete animal and continue to live as though nothing had happened. Slit a Hydra lengthwise through the tentacles and down to the foot, but without quite detaching the two parts. If left alone they will unite and form a perfect being again. Keep them asunder and two Hydras will be perfected on one foot. Slit a Hydra upwards to the base of the tentacles and keep the two portions apart; two bodies will be formed surmounted with but one pair of tentacles. Put the body of one into the mouth of another, keep them in position, and they will firmly unite and form a single animal, distinguishable from others only by the double number of tentacles. Cut a tentacle off and a new body and the remaining tentacles sprout from it. This extraordinary power is very wonderful, but never in a natural state does it employ this method of "fission" for reproducing its kind. It was formerly reckoned that a Hydra could be turned inside out like a glove, and continue to live and digest its food in this condition; but more modern researches have disproved this statement and shown it to be a fallacy. Such, then, is an outline history of what is veritably a green water-dragon.

BOTANY has made rapid advances within the last twenty years, and perhaps there is no cheap "Manual" published at that time now in active use except Dr. M. C. Cooke's "Manual of Structural Botany" (London: W. H. Allen & Co.), of which the 37th thousand (revised edition) has just been published. It contains fifteen illustrations.

SCIENCE-GOSSIP.

GERMS, poisonous and innocent, seem to be present everywhere. On their microscopic backs is placed the onus of a hundred diseases. A fresh one has just been added to the list. Tetanus, or "lockjaw," as that terrible affliction is more popularly called, is now proved to be due to the presence of a virulent micro-organism. Between the infliction of a wound and the development of lockjaw there is sufficient time to allow the spores of this minute organism to develop into bacilli, when the latter produce those distinctive features characteristic of this dreadful disease. The virulence of this organism is only equalled by its wonderful vitality. Thus a small fragment of wood was extracted from the ancle of a child who had died from lockjaw. This fragment was kept for eleven years, when a portion of it, by way of an experiment, was introduced under the skin of a rabbit, and the rabbit died immediately afterwards of tetanus. In the pus or yellow matter of the wound, made by introducing the splinter of tetanised wood, crowds of tetanus bacilli were found.

66

MANY of our readers are acquainted with the remarkable lens brought out by Mr. Dallmeyer during the present year, and which he calls telephotographic." This long word simply suggests the invention of a lens which can photograph objects at a distance. For instance, at a recent meeting of the Camera Club, pictures were exhibited representing all the details of a building which had been taken at a distance of 500 yards. Two cameras seem to be necessary, one supplied with a long focus landscape lens, and the other with Mr. Dallmeyer's new telephotographic lens. In this way the flame of a common oil lamp placed twenty feet away can be accurately photographed. It is anticipated that before long this new lens will be applied to that deeply interesting department of modern scientific researchstellar-photography.

A NEW method of manufacturing glass vessels which will not break under sudden changes of temperature is announced; the plan adopted being to make the article with an inner layer having a lower co-efficient of expansion than the outer layer. Articles made in this way seem to have the useful qualities of Bastie's "hard glass," without the tendency to spontaneous explosion; and the making of them is in most cases easy, as the operator first takes up on his blowpipe a mass of the glass with the lower co-efficient of expansion, and the more expansive glass is now taken up on the outside of the first by dipping in another pot.

CHEMISTS rush in where angels fear to tread. To them there is nothing hidden that shall not be revealed. In their researches and experiments the word "sacred" is unknown. Here is an instance of

their daring. For ages the most valuable precious stone in the world has been the diamond. Of course it was known that this crystallised bit of carbon could be burnt like an ordinary piece of coal, if it were subject to a sufficiently high temperature, for Sir Isaac Newton demonstrated this more than two hundred years ago. Apart from this fact, however, the diamond was regarded as peerless amongst precious stones. It was the hardest object in the whole world of matter. Nothing could corrode it or destroy it. Alas! a German chemist, Mr. Luzi, has just demonstrated that. diamonds can be corroded by heating them for half an hour in the melted matrix or "blue ground," in which they are usually found in the South African diamond-fields; and it is thought that the process depends upon the reduction of the melted matrix or magma at the expense of the carbon of the diamond.

ONE of the most wonderful places in the whole world, for number and variety of metallic minerals is the "Broken Hill" district of New South Wales, recently noted for the bitter losses of the strike quarrel there. We possess at least a score of small specimens of various minerals from one particular mine in that neighbourhood. When the geological formation of all these various minerals, their origin, mode of occurrence, etc., comes to be written (as one day it must be) it will prove as interesting as the volume issued by the United States Government upon the Sierra Nevada district of Western America, out of which one of the owners, Mr. Mackay, is taking £25,000 a week. A new form of silver ore has just been discovered in the Broken Hill district. It consists of hard, horny particles of ore, containing traces of gold and silver, associated with traces of iodide, bromide and chloride. It has long been

suspected by some eminent mineralogists that seawater, in a highly heated form, or otherwise, has had a good deal to do with the deposition of precious metals, and the composition of this new silver ore will undoubtedly strengthen the belief. The water of the sea contains a good many metals, which its chlorides have enabled it to dissolve. How many people know, [for instance, that every cubic mile of sea-water contains fifteen tons of silver? The new silver ore above referred to is found disseminated through beds of fine clay, which have been subterraneously heated, so as to resemble baked kaoline or biscuit-ware.

MORE than a quarter of a century ago a book was written by the Hon. Mr. Marsh, United States Consul at Florence, entitled "Physical Geography as Influenced by Human Action." It gave a long list of instances in which the indiscriminate cutting down of forests had affected the rainfall of countries. Climate is an exceedingly sensative thing, and every leaf on every tree, shrub, and plant influences it. Vegetation is a marvellous regulator of climatic

conditions, particularly of rainfall. The latter is stayed and checked by the influence of the former. Cut down the forests of a country, and the rainfall becomes irregular; so, of course, does the volume and velocity of rivers, floods, and torrents. Such altered conditions bring about extremes of dryness and wetness. Let all the vegetation be cleared away and perhaps general aridity, and therefore sterility, are the results.

THE subject of the earliest eruptions of Mount Etna has recently been discussed before the Paris Academy of Sciences. They commenced in the Upper Pliocene period, represented in England by the shell beds which form the Suffolk and northern Essex cliffs. From that particular period, before the appearance of man on earth, right through the great northern ice age, Etna has been a living volcano, through long periods of time, which, although a mere skin-deep part of the antiquity of our planet, probably extend over a quarter of a million of years!

A VERY interesting paper by Mr. Dickson has just been published, in which he shows how the ebb and flow of tides in the English Channel are affected by the shapes or main features of the coast-lines. Thus, bays with a western side run nearly from south to north, turn at a sharp angle, and lie open to the east. Even the circulation of the water as well as the temperature Mr. Dickson found was largely influenced by the conditions.

ONE of the most important physical discoveries of our generation was demonstrated by Professor Dewar before a brilliant audience assembled in the Royal Institution. This was no less than the liquefaction of atmospheric air. All gases except hydrogen have now by compression and extreme cold been artificially liquefied. The air we breathe was the last to hold out, but now we are in front of the possibility of a liquefied atmosphere. In addition to the pressure used to produce atmospherical liquefaction, a cold equal to 327° of frost had to be employed. The liquefied atmosphere is of a faint blue colour.

A VERY destructive earthquake occurred in the island of Zante on January 31st. The shocks were frequently repeated.

AUSTRALIA is about to grow its own tobacco. It is surprising the colonies never thought of it before !

WE are pleased to draw the attention of our archæological and geological readers to Mr. John Allen Brown's paper (illustrated) reprinted from the "Journal of the Anthropological Society," entitled "The Continuity of the Paleolithic and Neolithic Periods." Mr. Browne is well known as an excellent observer and ardent collector, and he makes out a very good case.