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Plants' used it for his two subtribes of Arethuseæ. I am inclined to re-establish Blume's Epiphanes, which differs in habit from Gastrodia sesamoides, R. Br., as figured in Hooker's Tasmanian Flora. The fruit, too, seem to be different, though those of the Australian plant are only insufficiently known. Gastrodia is said to be epiphytical, whilst Epiphanes is certainly terrestrial.

I must leave it an open question whether G. Javanica, Lindl., and G. Hasseltii, Bl., are distinct species or not, not having that part of Blume's work to refer to. According to the diagnosis in Miq. Fl. Ind. Bat., however, the Griffithian plant should be referred to G. Hasseltii, this having a rugulous crista. The characters of the more or less acuminate sepals appear of doubtful importance, our Bengal plants having them both acute and obtuse. Thwaites refers his Ceylon plant to G. Javanica, and I think correctly.

If Epiphanes should be incorporated with Gastrodia, the sections would be better defined by relying upon the situation of the stigma rather than the labellum, as Professor Miquel has done.

Highly interesting are the pedicels of D. pallens. Originally they are only 2-6 lin. long, but when the fruit becomes fully ripe, they elongate and are often twice as long as the whole plant. I measured one more than a foot long and rather thicker than the scape. The bracts vary much, and they are largest in the smaller plants.

The plant varies in height from 2 to 10 inches; and if my identification of G. Javanica and Hasseltii. proves correct, it ranges over Java, Bengal, Ceylon, and Coorg.

Botanic Garden, Calcutta, Nov. 30, 1865.

ON ANADYOMENE AND MICRODICTYON, WITH THE

DESCRIPTION OF THREE NEW ALLIED GENERA, DISCOVERED BY MENZIES IN THE GULF OF MEXICO.

By Dr. J. E. GRAY, F.R.S., V.P.Z.S., F.L.S. The subject of this paper has interested me for nearly half a century. I was so struck with the figure of the genus in Lamouroux's work, that I was very anxious to be able to examine it My late dear friend Edward Bennett and I, purchased all the “ Mousse de Corse" we could find in London, and searched it most industriously, but without effect. I was therefore greatly pleased when, many years after, Professor Harvey most kindly gave me a series of the species he had found in Florida, which I could study at my leisure, and I found it as beautiful as I had anticipated.

Having recently had occasion to examine the specimens of the genera Anadyomene and Microdictyon, in the botanical collection of the British Museum, I was much interested in two specimens which were collected by my very kind friend, Mr. Archibald Menzies, in the Gulf of Mexico, in the year 1802, which appear to this time to have been undescribed. One is allied to, but very distinct from, the genus Anadyomene of Lamouroux, and is a giant of the tribe. The other is allied to Microdictyon, a genus established by M. Decaisne, but differs from it in the frond being free, and on a filiform conferva-like branched stem, the leaf-like frond bearing a resemblance to the frond of Struvea of Sonder and Harvey.

The Anadyomene has long been known; it was figured by Dillenius; Wulfen described it as an Ulva, and the genus was established by M. Lamouroux as a zoophyte, from some specimens which he found in the “ Mousse de Corse" in the stock of a druggist in Normandy. It is now well known to be an Alga.

The form and structure of Microdictyon was well described and figured by Colonel Velley in 1799, and his figure is the best, except Harvey's, that we yet have ; but he referred it to Conferva—that magazine for the articulated Alga.

Professor Endlicher, in the third supplement to his 'Genera Plantarum,' formed the genus Anadyomene into a subtribe, under the name Anadyomenea, p. 18.

Kützing, in his ' Species Algarum,' 1847, forms of the genera Anadyomene and Microdictyon a family, under the name of Anadyomenea, p. 371, referring to it the genus Talarodictyon of Endlicher, but with doubt. I do not know the latter genus ; indeed, it is only described from a figure in the MS. of Tilesius.

Professor Harvey, in his very useful `Index Generum Algarum,' 1860, refers the genera Microdictyon and Anadyomene with Struvea, as genera of the family Valoniacea, p. 13.

There can be no doubt that the two genera belong to two very distinct groups, perhaps to distinct families, but this cannot be determined until the fructification and habits of the two genera have been studied; the chief difference between the two groups being that one has the lines of cells united by their sides, so as to form a membranaceous frond, and the other the cells isolated from each other, forming a net with open polygonal meshes, as pointed out by M. Montagne.

There is a certain amount of resemblance between the fronds of the Microdictyonea and those of Struvea ; but the cells which form the frond of Microdictyon and the stem especially from which the frond of Phyllodictyon arises, are much more like the cells of the filament of a Conferva than of a Dasycladus ; on the other hand, Struvea, in its structure and mode of growth, is very nearly allied to the unicellular Alge. The stipes and the midrib or axis of the frond is a simple onecelled continuous tube, very unlike the slender articulated stem and midrib of Microdictyon and Phyllodictyon. Indeed, it appears to me that the stem, the midrib, and the cells that form the reticulation of these two genera are very similar to the cells which form the filament of Cladophora, and it would appear that the tribe is more allied to Confervaceæ than Valoniaceæ.

GROUP I. ANADYOMENEÆ.The frond membranaceous, formed

of articulated forked or digitate proliferous filaments, the inter

spaces between the branches filled with polygonal cells. This group consists of three genera : one, the Anadyomene of Lamouroux; one, very like the former genus in appearance, discovered in Australia by Mr. R. Brown; and the third, founded on a beautiful Alga, which the late Mr. Menzies discovered in the Gulf of Mexico, and named Anadyomene Menziesii by Dr. Harvey.

This A. Menziesiï has the interspaces filled up, as in Anadyomene, but in that genus the main ribs of the frond are formed of a single series of articulations like a Conferva, while in the Conferva umbilicata of Menzies the main stem is formed of several transverse series of cells condensed into a midrib, differing in this respect from all the other genera of marine Alge.

The genus is evidently the plant referred to by Professor Harvey in the following terms :--" The largest specimen I possess was given to me by the late Mr. Menzies, as having been dredged in twenty fathoms in the Gulf of Mexico. This specimen measures 6 inches, and its venation offers some peculiarities which perhaps may lead to its specific separation. In our Key-West plants the seriated cells of the principal veins stand apart from each other, or are in single file, having wedgeshaped spaces between. In Mr. Menzies' specimen the principal veins are partly unicellular, partly formed of several parallel closely-placed cells without interspaces; the structure is easily seen, but difficult to describe in intelligible language. Should subsequent observation establish this plant as a species, it may be called A. Menziesiz.(Harvey, Nereis Boreali-Americana, iii. 50.) I did not discover this observation until after I had described the genus; and I may observe that the simple series of cells is only found, in the larger specimens in the British Museum, in one or two of the smaller lateral branches near the circumference of the frond; all the others are formed of fan-shaped series of cells, from three to five being in each cross-series, and I am more confirmed in this opinion, as I believe there are more than one species of the same form with the typical Anadyomene from very different localities, which may be characterized by the form of the cells, and all these species agree in having the main stem formed of a single series of cells very unlike the many-cellular midribs of Mr. Menzies' species from Mexico.

It is to be observed that Montagne, when he first observed the Microdictyon, called it a second species of Anadyomene, and the character that he gave to distinguish the species was used by Decaisne to separate the two genera, and it is quoted by Kützing as the specific character of the species of Microdictyon, although it was drawn up to distinguish it from A. stellata.

I may perhaps be regarded as unwise in forming a genus of a plant that Professor Harvey regards even as a doubtful species. I have not done so without great consideration; but when I know that there are at least four, if not more specimens of Mr. Menzies' Mexican plant in collections, viz. the one in the British Museum, one at Kew, one in Dr. Harvey's collection at Trinity College, Dublin, and one or more in Mr. Menzies' own collection, which he left to the Edinburgh Botanic Garden, I cannot but regard it as a distinct form ; indeed, Professor Harvey, in a note lately received from him, admits its being so.

Now, if it is a distinct plant, as it presents a very different organization to the other species, which it undoubtedly does, surely that is enough to form it into a genus. I believe that it is a genus likely to meet with the approval of botanists, or I should not give to it the generic name of Grayemma, which, at the suggestion of Mr. Bennett, I propose to do,--that being a combination of the two names of my wife, who has been my companion and helper in all my studies for forty years, and who has some claims to be regarded as a botanist, as for several years she has studied seaweeds not only in the herbarium but in the living state, and has acquired such a knowledge of them that the late Sir W. Hooker entrusted her to arrange the British Alge in the Kew collection; and Mr. Bennett, first to arrange the British, and then the general collection of Alge in the Herbarium of the British Museum. The combination of the two names as a generic one is almost a novelty, but it appears to me that the termination of -emma is as pleasant-sounding as the usual diminutive of -ella, and in this case more determinative. The name of Grayia has been already used in honour of Professor Asa

Gray.

SYNOPSIS OF THE GENERA. Genus 1. CALOMENA.-Filament of frond formed of linear joints, furcately-branched to the end of the frond; disk of the frond minutely cellular.

Genus 2. ANADYOMENE.—Filament of the frond formed of ovate cells with diverging cells on the tip, some of which are proliferous, and with cells on the sides; the disk of the frond with regularly disposed small cells.

Genus 3. GRAYEMMA.—Midrib of the frond formed of several parallel series of cells, the terminal bearing radiated cells on their tip, and the disk of the frond formed of diverging cells.

Genus 1. CALOMENA. The frond coriaceous, flabellate, imbricate at the base, formed of a

succession of single elongated cylindrical cells which separate at the tip into two or rarely three similar cells, and forming a succession of forked (rarely at the lower part of the frond trifid) branches to the margin of the frond; the cells diminishing in length as they approach the margin ; the interspaces between the cells minutely cellular.

This genus is most distinct from Anadyomene. It is like the furcately-branched Valonia, called Ascothamnion, expanded and united together into a frond, but the disk of the frond shows none of the

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