404 MR. B. CLARKE ON THE EMBRYOS OF ENDOGENS 
furrow on its surface, as in Avena and Hordeum. 'The embryo of Hordeum vulgare is in 
this character much like that of Cymodocea Webbiana, as figured by Ad. de Jussieu*, the 
position of its leaves being precisely the same; so that the evidence of the identity of the 
embryo of Zostera with those of the Graminaceæ appears to be complete, and the com- 
paratively large radicle of this genus and its allies may be regarded as supplying the place 
of the deficient albumen. 
As a further argument that the apparent cotyledon of the Graminacee is a radicle, it 
deserves remark, that in germination it scarcely enlarges, and its smaller lobe, by some 
botanists regarded as a second cotyledon +, also remains almost stationary; whereas the 
stipulary process of the cotyledon, which occupies the same position in Smilacina, Tamus, 
Tris, and Canna, grows in favourable circumstances so as to be as long or longer than the 
cotyledon, or even as long as the seed, and sometimes forms a sheath for the young stem. 
In this view of the structure of the embryo of the Graminaceæ, the second or rudiment- 
ary cotyledon, which is a minute body, usually referred to as being alternate with, and 
rather lower down than the larger (fig. 20 5), is the smaller lobe or process of a two-lobed 
radicle, as in Zostera (fig. 8 a) ; so that the division of flowering plants by Ray into Mono- 
cotyledonous and Dicotyledonous is quite correct, and the Endogens are separated from 
the Exogens more completely by this character than by any other. | 
For the purpose of further explanation as regards the germination, the position of the 
first leaf of the plumule, and a proposed division of the Endogens, particular notices of the 
embryos of the families examined are added. | 
Cyperacee.—I have seen germinating the seeds of Cladium Mariscus, of a Cyperus, 
and of a Carex from Japan, and find that they agree with the Graminaceæ in having the 
first leaf of the plumule always next the cotyledon, as at present understood, from which, 
as this family is so nearly allied, it may be inferred that the embryo has the same struc- 
ture, and therefore consists of a radicle partially enclosing a cotyledon. There is nothing 
in the germination to contradict this supposition, unless it is that the radicle is endo- 
rhizal in the lowest degree, as no coleorhiza forms, and the nascent spongiole emerges 
from beneath the surface without a distinct appearance of a rupture of tissue taking 
place. This is the only family I have observed to agree with the Graminacee in the 
altered position of the first leaf of the plumule, but it not improbably occurs in other - 
glumaceous Endogens, as Restiaceæ and Desvauxiacee. 
Zosteracee.—The embryo of Zostera marina has been accurately figured by Richard }: 
the cotyledon is seen elevated on a cauliculus, and the position of the plumule is distinctly 
shown, and even the smaller lobe or process of the radicle is faintly indicated, but it 
is imperfectly seen in consequence of the embryo being closed; but its endorhizal cha- 
racter does not appear to have attracted notice. This, however, is quite obvious, as the 
* Ann. des Sciences Nat. 2"* série, xi. Bot. pl. 17. fig. 16. 
s : T ieri nun that this is not a second cotyledon, but a part of the cotyledon itself, which beoe pi 
à T and Mate It as being of the same nature as stipules, to which it certainly has a close resemblance ; but, as 
oes not enlarge in germination, it wants one of the characters of stipulary processes, as far as my observation has. 
race. (Vide Sehleiden's Principles of Scientific Botany, translated by Dr. E. Lankester, p. 272.) 
f Ann. du Muséum d' Hist. Nat. tom. xvii. pl. 9. figs. 47,48. | 
