Milde states, that he has observed the motion of the spermatozoa to last from morning till night. Dr. Schacht on the contrary says, that such motion seldom lasts more than two hours. He attempts to reconcile his own observations with those of Milde, by the suggestion that fresh spermatozoa may be continually produced from the same prothallium, and thus supply the place of those whose motion has ceased. Without knowing what precautions were taken by Milde in his experiments, it is impossible to say whether this explanation can be accepted. It can hardly be doubted that variations of temperature and light exercise sufficient influence to account for great variations in the duration of activity, if not for so much difference as that between these two authors.

Dr. Schacht gives full particulars of the effects of a number of chemical re-agents. We have not space to follow him in detail, but may state generally that he considers it to be proved-1. That cellulose exists in the membrane of the mother-cell of spermatozoa, either specially modified, or in combination with substances of a similar nature; 2. that nitrogenous matter is present in the membrane and in the cilia of the spermatozoa, and probably also in a fluid form in the cell-sap; 3. that the cell-sap itself contains starchgrains.

Dr. Schacht's observations on the spermatozoa of Ferns were made upon the following species, Doodia dives, Gymnogramma pulchella, Pteris serrulata, Adiantum formosum, and Asplenium Petrarcæ. He is of opinion that these spermatozoa are not so well suited for deciding questions of structure as those of the Equisetaceæ, but that when compared with the latter the conclusion is the same, viz., that the spermatozoon is a cell.

The peculiarity and wonderful beauty of the antheridia of Chara and Nitella are well known to all cryptogamists. The mother-cells of the spermatozoa, hanging in alga-like threads to the valves of the antheridium, are amongst the most curious productions of the vegetable kingdom. Dr. Schacht does not add much to what had been previously noticed, but he considers that correct observation of the spermatozoa will show conclusively that the terminal enlargement, visible here, as in other spermatozoa, is a true vesicle, and not a flat membrane as suggested by Hofmeister. With regard to the formation of the spermatozoa of the Characeæ, Thuret's opinion was that such formation takes place from the apex of the antheridial threads backwards, whilst Mettenius alleges the reverse to be the

case. It is to be regretted that Dr. Schacht confesses his inability to give an opinion one way or the other. We think that Mettenius

is probably right, but Thuret is generally so accurate that it is difficult to be confident.

Amongst other points here discussed we find allusion to the question, first started we believe by Meyer, that the spermatozoon is formed from the nucleus of the mother-cell. The observations of Mettenius and Hofmeister tend to this conclusion, which is fully confirmed by Dr. Schacht.

The spermatozoa of the Mosses and Liverworts, the Lycopodiacea, Rhizocarpeæ, and Algæ, are but slightly noticed in the present work, and there is nothing of sufficient novelty or importance to call for any detailed remarks. The statement that in Alge the spermatozoon has the form of a small cell, either round and elongated, or acuminate at one end, is somewhat too general, being hardly applicable to such spermatozoa as those of Vaucheria and Sphæroplea.

In summing up the principal results to which his observation led him, Dr. Schacht makes the following remarks upon the typical forms of spermatozoa: he says, "We can therefore distinguish in cryptogams three typical forms of spermatozoa, viz., a. The type represented by the Alga. b. The type of the Equisetacea; and c. that of the Characea; and there is, moreover, as regards germination and the appearance of the sexual organs, a close relationship between the families belonging to one type. Thus in the Alga we have the simplest sexual organs and direct germination; in the Equisetaceous type (the Equiseta and the Ferns), on the other hand, we find complicated sexual organs produced upon a prothallium, or if we include the Lycopodiacea and Rhizocarpeæ, we have female organs only upon the prothallium. Lastly, in the type of the Characea (the Characea, Mosses and Liverworts) the sexual organs which are similar in structure occur upon the developed plant, but in the place of direct germination we have the spore producing a pro-embyro, upon which, and from a bud, the young plant originates. The Characeous type occupies the middle place between the types of the Algae and the Equisetaceœ."

LXIX. RECENT WORKS ON THE EQUISETACEÆ.

(1.) HISTOIRE NATURELLE DES EQUISETUM DE FRANCE. Par J. Duval-Jouve. Paris. 1864.

(2.) EQUISETACEE. Auctore Dr. J. Milde, Vratislaviensi.-Conspectus Equisetorum omnium secundum affinitatem naturalem dispositorum. Annales Musei Botanici Lugduno-Batavi. Tom. I. Fasc. II., III., VIII.

THE above-mentioned work of M. Duval-Jouve, is one of the most interesting and important contributions to cryptogamic botany that has appeared for some time past. In the report of the distinguished botanists, to whom the work was referred by the French Academy, it is spoken of in the following terms:-"L'histoire naturelle des Equiseta de France, par M. Duval-Jouve est un des travaux les plus complets qui aient jamais été fait sur une famille naturelle, assez limitée, il est vrai, mais des plus remarquable par sa structure. Les études anatomiques et organogéniques si etendues et si exactes que ce Memoire comprend lui donnent un caractère plutôt physiologique que de botanique purement descriptive.

The work is divided into two parts-the first relating to the anatomy and reproduction; the second to the classification and description of the plants. We will refer to the latter part first.

The chapter on the history and synonymy of the species takes us back to the Pinax of Bauhin, who in 1623, and again in 1658, in his Theatrum Botanicum, arranged thirteen plants, which he called Equiseta. One of these however being Elatine Alsinastrum L.; another Hippuris vulgaris L.; and a third some species of Chara, only ten are left which can be referred to the Equiseta, and some of these M. Duval-Jouve considers to be very doubtful. Fifty years afterwards, Tournefort in his Institutiones, established the genus Equisetum, from which the Chara were separated by Dillenius.†

The descriptions given by Linnæus in the Species plantarum, included six European species of Equiseta (or five, if Eq. limosum and Eq. hyemale are identical); but M. Duval-Jouve considers that the Linnean herbarium does not afford materials for determining with certainty Linnæus' specific types.

Vaucher's Monographie des Préles, published in 1822, must be

MM. Decaisne, Tulasne and Brongniart.

Duval-Jouve, p. 227.

looked upon as the foundation of the modern classification of the species of Equiseta. We have not that work by us, but the substance of his (Vaucher's) arrangement, as well as of the subsequent ones proposed by Al. Braun, are given by M. Duval-Jouve, at pp. 231-33. Vaucher states that the character of primary importance is the existence of a fruiting stem (which he calls une hampe), distinct from the barren stem; the second character is the number of teeth in each sheath; the third the nature of the stem, which is sometimes cylindrical, sometimes more or less angular, sometimes smooth, sometimes rough; the fourth character is the regu larity of the branches; and the last that of the stomata, or as he calls them, the glandes corticales. Speaking of these latter, Vaucher observes that the species (of Equiseta) differ much amongst themselves in the number and disposition of these glands. Some, such as E. sylvaticum, umbrosum, and fluviatile, are almost devoid of them; others, such as E. palustre, possess them in abundance. In certain species he adds they are scattered (eparses), in others arranged in regular order.

Some years later (in 1838), Professor Al. Braun proposed his arrangement of the European species, in which he divides the Equiseta primarily into two groups. 1. HETEROPHYADICA, characterised as having dimorphic shoots, the fertile ones appearing early, the barren (frondescent) ones at a later period. 2. HOMOPHYADICA, having uniform frondescent shoots, the barren and fertile being alike and contemporaneous, or all being fertile. The first group is again divided into Ametabola, having the fertile shoots not frondescent, and which soon disappear; and Metabola, where the fertile shoots are persistent, and ultimately send out leafy ramuli. The second group is divided into those with annual shoots, dying in the winter, and those with evergreen shoots, which survive the winter. Afterwards, in 1843, Professor A. Braun published a new mode of arrangement, in Silliman's American Journal of Science and Arts, in which he divides the plants into SPEIROPORA (or those in which the stomata are scattered), and STICHOPORA, where the stomata are arranged in regular order. As M. Duval-Jouve remarks (p. 233), Braun's classifications are in effect identical with those of Vaucher.

Milde takes the nature of the stomata as the primary character in his arrangement. He divides the Equiseta into PHANEROPORA, where the stomata are in the same plane as the epidermis; and

N.H.R.-1864.

2 P

CRYPTOPORA, where the stomata are situated beneath the epidermis, which is perforated above them. The Phaneropora are divided into heterophyadica and homophyadica (Braun's primary divisions): the heterophyadica are subdivided into a. Equiseta anomopora, and b. Equiseta stichopora; and the homophyadica are divided into a., those whose branches have no central cavity, and b., those in which such cavity is present.

We proceed to state M. Duval-Jouve's arrangement of the Equiseta, as given in the work before us, and the reasons which he gives for the alterations which he proposes. He divides the genus into two sections, and each section into two groups, as follows:

1ST SECTION. Stems not contemporaneous, dimorphic: the fertile ones appearing first: the barren ones later, always branched, the branches having a central cavity.

1st Group.-Internodes of the barren stems white, having the epidermis entirely devoid of stomata.

2nd Group.-Internodes of the barren stems more or less green, with stomata on the epidermis.

2ND SECTION. Fertile and barren stems contemporaneous and alike in form; the branches of the stems (when present) furnished with a central cavity.

3rd Group.-Spike not apiculate; stomata scattered in the furrows; ostiolum of the stomata level with the epidermis.

4th Group.-Spike apiculate; stomata arranged precisely in single line on each of the ridges of the furrows; ostiolum of the stomata at the bottom of an irregularly-bordered cavity.

The eleven French species fall into the Groups as follows:-1st Group, E. maximum Lam.; 2nd Group, E. sylvaticum L., E. pratense Ehr., E. arvense L.; 3rd Group, E. littorale Kühl., E. limosum L., E. palustre L.; 4th Group, E. ramosissimum Desf., E. variegatum Schleich., E. trachyodon Al. Br., E. hyemale L.

The grounds upon which this arrangement is proposed are thus stated. The author says:

"The first character which I have taken for the division into sections, is the conformity or non-conformity of the fertile stems. And this, in the first place, because this character, which is easily appreciated and constant, does not consist of a simple superficial difference, but is connected with considerable differences of constitution and function. It has also an organic and physiological value; and, lastly, all the species which it unites resemble one another more closely than they do any of those from which they are separated.