"Each of the two great sections thus arrived at is divided into two groups, the first distinguished by the absence or presence of stomata; and the second by the form and distribution of the latter. These characters, which appear at first difficult to realize with the naked eye, are by a happy accident always accompanied by other characters very easily appreciated. Thus in the first section the presence or absence of stomata is necessarily indicated by the presence or absence of the green colour on the internodes, and in the second the dispersion of the stomata on the furrows of the internode, or their exact arrangement in two parallel lines, the situation of the ostiolum of the stomata, on a level with the epidermis, or at the bottom of an irregular cavity, are indicated, the latter by an acuminate, the former by an obtuse spike." We will now refer to a few details, in which the author's views differ from those of other botanists. Mirbel considered the sheaths of Equiseta to be formed of leaves united together, the teeth or lobes being the free extremities of the leaves. This hypothesis is admitted by M. Duval-Jouve to be that which most naturally suggests itself, but he observes, that when it is remembered, on the one hand, that the lobes are not really free, and that they only appear so in consequence of a rupture of the sheath, produced mechanically by the growth of the internode which it covers, and when it is remembered, on the other hand, that the leaves are essentially aerial organs, and that the rhizomes are furnished with sheaths as regular and as well-developed as those of the stem, the conclusion is that the lobes cannot be regarded as leaves, and he determines to speak of them only as "divisions de la gaîne." M. Duval-Jouve objects to the use of the term pro-embryo or prothallium, the latter of which is usually employed to designate the organ produced by the germination of the spores. He uses instead the term "sporophyme," a term suggested by himself as long ago as 1859,* and defends it by saying that the Equiseta have neither thallus nor embryo, properly so called. It seems hardly worth while to attempt to displace established terms upon such strict technical reasoning, and this appears to be the opinion of botanists, for the word "sporophyme" has not yet been admitted into botanical terminology. In discussing the nature of the tissue of the tubercles, which occur on the rhizome, it is said (p. 41.) that the mass of the cellular tissue is composed of cellules of some size, much shorter than in any other part of the rhizome or the stem, and containing a great quantity of *Sec Bull. Soc. Bot. Fr. vi. p. 704. amylaceous granules, and some traces of sugar. Hofmeister speaks of the tubercles as containing a great deal of sugar, a statement somewhat confirmed by an amusing extract from Helwing, given by M. Duval-Jouve himself, at p. 7 of the present work. Helwing says, under the title of Equisetum arvense glandiferum: "Hujus radicibus glandes copiose adherent, et quam maxime in agris arenosis effodiuntur a suibus et pueris rusticis. Grati et dulces sunt saporis. Instinctu naturæ sues odoratum superficiem terræ detegunt, et tam diu terram evolvunt, quod appropinquent ad glandes Nostratibus Erd-nüsse dictos, quod subulci animadvertentes statim accurrunt, et pedibus porcos abigentes levissimo labore nucleos suos terrestres colligunt." We have heard of employing pigs to hunt for truffles, but are not aware that the tubercles of Equisetum arvense, which must be plentiful enough in this country, are ever sought after either by boys or pigs. In his treatise on the higher Cryptogamia, Hofmeister remarks* that numerous obstacles seem to interfere with the natural germination of the Equisetacea. He says, that although he has often searched for them, he has never found the prothallia of any species in their natural state. M. Duval-Jouve's experience seems to be in conformity with this, for he speaks of having found the prothallia of E. arvense for the first time in July, 1860, in a peat-moss near Haguenau. At the spot where they occurred, they were found, as might be expected, in thousands. The usually dioecious nature of the prothallia of the Equisetaceæ, has been noticed by Hofmeister and by Milde. M. Duval-Jouve observes, that although it is very unusual to find antheridia on female prothallia, the tendency to diœciousness is not reciprocal in the antheridial prothallia, for he says that it is not rare to find archegonia towards the base of the ramifications of the male prothallia. He adds, however, that such archegonia have always seemed to be barren. With regard to the male and female prothallia, Hofmeister has remarked that the spores from which they originate, are exactly of the same size and quality, and that external circumstances seem to have an influence upon the germinating prothallia; that for instance in E. arvense, a dry place exposed to light seems decidedly to favour the development of male prothallia. We have some doubt p. 296. Hofmeister on the Higher Cryptogamia, Ray Society's Edition, 1862, whether we clearly understand the meaning of M. Duval-Jouve's remarks as to the production of male and female prothallia. He alludes to Hofmeister's remarks, citing them however from the transactions of the Royal Society of Saxony, without noticing the fact of their having been republished several years later in the Ray Society's (1862) edition of the "Vergleichende Untersuchungen ;" and he then remarks: j'incline volontiers a croire que l'action des circonstances extericures se borne à arreter ou à favoriser le developpement des sporophymes de l'un ou de l'autre sexe, dont la vigueur est d'ailleurs si differente, sans aller jusqu'a une influence de determination de sexe sur un sporophyme en vegetation." With regard to the way in which the obstacles to fecundation arising from the dioecious nature of the prothallia are overcome, there is no difference of opinion between the two last named writers. The male and female prothallia grow in close proximity, owing to the interlacing of the spores by the entanglement of their elaters, and thus access to the archegonia is afforded to the spermatozoa, not only by rain and dew, but also by the force with which on the spontaneous opening of the antheridia the spermatozoa are ejected.* We do not find any thing new in the account of the form and general structure of the spermatozoa of the Equisetaceae beyond this, that M. Duval-Jouve's observations on the mother-cells (as far as they go), tend rather to confirm the views lately expressed by Dr. Schacht in his work "Die spermatozoiden im Pflanzenreich." For comparison with Dr. Schacht's remarks, we extract the following from pp. 103-4, of the work before us. "As to what becomes of the cellules or rather the globules after the spermatozoa have become disengaged normally and completely, I am ignorant; I have never seen the slightest traces of these empty cellules, perhaps because their substance is dissolved in the water, or perhaps because what remains of them is invisible on account of its perfect transparence and extreme tenuity; or lastly, perhaps, because nothing appreciable remains behind, the cellule being absorbed in proportion as the spermatozoon is formed. I incline the more to this opinion because at the moment of their becoming free, I have never seen the spermatozoa issue from their cellule and leave it, but these cellules seem to open and to be transformed into spermatozoa. Those which remain partly entangled in their cellule, would according to this view be those which are imperfect, and which have not entirely absorbed the cellule." *Hofmeister, op. cit. p. 300, Duval-Jouve, p. 108. M. Duval-Jouve's work contains ten beautifully executed plates, and we would direct special attention to the ingenious use of the layers of tracing paper in illustrating the structure of stomata. They are to be found in Plate IV. figs. 1 and 7, and in Plate V. fig. 1. The long list (amounting to nearly 100) of books and papers of different authors given, at pp. 277-280, forms a most useful bibliography of the Equiseta. To that list should now be added (besides the work of M. Milde, mentioned at the head of this article) the following recent publications, viz.: MILDE, "Ueber exotische Equiseten," in the Verh. der k. k. Zoologisch-botanischen Gesellschaft in Wien, xi. Band, p. 345. MILDE "Ueber Equiseten," op. cit. xii. Band, p. 1241; HOFMEISTER on the Higher Cryptogamia, (Ray Society's Publication, 1862), Chapter viii. pp. 267-306, and MILDE. "On the geographical distribution of the Equisetacea" in Seemann's Journal of Botany, Vol. I. p. 321. Milde's paper, "Ueber exotische Equiseten," contains some remarks on the value of microscopic characters in determining species which will be interesting to students of the Equiseta, and with which we will conclude our review; he says: "The importance of microscopical characters in distinguishing species will be appreciated by any one who will take the trouble to compare two species one with the other. These characters form the second distinct moiety of each diagnosis. Especial attention should be directed to the siliceous covering of the furrows of the branches, in which very closely allied species differ from one another. In order to see these siliceous prominences clearly, the best plan is to place the branch under the microscope in such a position that one of the furrows forms the outer margin of the object, and so that the projections appear as continuations of the margin. It is only necessary for this purpose, to compare the furrows of the branches of E. arvense, E. Telmateia, E. sylvaticum, and E. pratense under a magnifying power of 150-200, and the observer will easily see what striking differences are exhibited by these several species." LXX.-FRESENIUS' CONTRIBUTIONS TO MYCOLOGY. BEITRÄGE ZUR MYCOLOGIE, von Georg Fresenius, M.D. Drittes Heft, mit 4 Tafeln. Frankfurt, A.M. Brönner. 1863. AFTER a lapse of eleven years, Dr. Fresenius has published the third and concluding part of his Beiträge zur Mycologie. It will be of considerable interest to those Mycologists who are occupied in the study of the Mucedinous fungi. Twenty-nine species are described, 12 of which are said to be new, and for 5 of the 12, new genera are proposed. We will comment upon such of the plants as require notice in the order in which Dr. Fresenius describes them. Aspergillus fumigatus, Fresen., is supposed to differ from A. nigrescens Robin. in the green colour of the spores, and in the want of septa in the threads of the mycelium. Age, however, makes a great difference in the colour of the spores in Aspergillus, and it seems that the septa in the threads, although not usually met with, do occasionally occur, so that A. fumigatus may be said to be a doubtful novelty. Sterigmatocystis sulphurea, Fresen., belongs to a genus too nearly allied to Aspergillus. Isariopsis (a new genus) seems to be a Dactylium modified by the pressure of the cells of the stomata upon the flocci of the mycelium. Of Unger's obscure and unsatisfactory genus Ramularia, five species are described. Bonorden speaks of Ramularia as a "freies Caoma," and R. Urtica has been described as an Oidium. The species are probably not autonomous, and we cannot help thinking that the same may be the case with the author's new genus Cercospora, the so-called spores of which bear a suspicious resemblance to mere prolongations of the mycelium. It (Cercospora) approaches Helminthosporium, but there are grounds for supposing that this latter genus is only a conidioid state of certain Sphæriacei. Passalora bacilligera, Fr. was first described by Montagne as a Cladosporium, and is doubtless (as Dr. Fresenius remarks) closely allied to Cercospora, whatever that genus may represent. Chatocladium is a genus proposed for the reception of Botrytis Jonesii, B. and Br. We wish that the author had given his reasons for this removal. Although somewhat abnormal in structure, the plant might well have remained in the genus Botrytis where it had been placed by Messrs. Berkeley and Broome. Its pseudo-parasitical habit, if correctly observed, is an interesting fact, but affords no argument for removing it from Botrytis. Unless the shape of the spores is a sufficient generic distinction, Amblyosporium Fresen. (another new genus) does not appear to differ materially from Stachyobotrys. The description of a number of Coniothecia is succeeded by some remarks, in which we quite concur, as to the difficulty of distinguishing the species, and as to the close affinity of Coniothecium with Septosporium, Monosporium, Stemphylium, &c. The work concludes with the account of a monstrosity for which the fifth new genus is formed, • Annales des Sc. Nat. 1836. |