402 MR. B. CLARKE ON THE EMBRYOS OF ENDOGENS 
marina the radicle is readily discernible lying in a canal directed obliquely towards the 
apex of the seed. 
Although the germination of the Endogens is as yet known only in part, the subjoined 
instances of the exorhizal character occurring among them will, I believe, lead to the 
anticipation that the endorhizal is the exception rather than the rule, as most of those 
families in which the germination is unknown scarcely differ from one or other of the 
following, in which the primary radicle, as far as my observations have extended, is 
strictly exorhizal :—Liliacee, Dioscoreaceæ, Juncagineæ, Alismacee, Butomacee, Iridee, 
Amaryllideæ, Orchidee, Palmacee, Aracee, Typhacee, and Briocauloneæ *. 
The inquiry relating to the position of the first leaf of the plumule originated in 
having observed that in the Graminacee the first leaf of the plumule is next the coty- 
ledon, whilst in all other Endogens I had seen germinating it was directly away from the 
cotyledon, so as to be alternate with it, as in the ordinary genera of Liliaceous plants. 
For some years this phenomenon had appeared inexplicable, but further comparisons 
have led to the conclusion that the suggestion of L. C. Richard, as regards the embryo of 
the Graminacee, viz. that the apparent cotyledon is in reality an enlarged radicle, is the 
only practicable explanation of this departure from the regularly alternate position of the 
leaves of the embryos of the Endogens. But as objections exist to regarding the apparent 
cotyledon of the Graminacee as the radicle or a part of it, it may with equal propriety be 
compared to the enlarged cauliculus occurring in exogenous plants, or to the cormus as 
occurring in endogenous plants, and then the first leaf of the plumule will be the coty- 
ledon, containing within it the leaves of the plumule occupying their usual alternate 
position. For the purpose, however, of being more readily understood, I shall, with 
Richard, still call it a radicle, though at first sight this view does not appear at all pro- 
bable ; but yet the position of the first leaf of the plumule next the apparent cotyledon in 
Graminacee and Oyperacee (fig. 20 c) appears otherwise an anomaly not to be accounted 
for. But admitting that the cotyledon, as at present generally understood, is either an 
enlarged radicle or a cormus, the steps by which such an inference may be arrived at 
form an almost unbroken chain. ~ 
Beginning, for example, with Caulinia, Naias, and Potamogeton, we find that the first 
leaf of the plumule alternates with the cotyledon, being directly away from it; and the 
embryo does not otherwise differ materially from those of Orontiacee, Aracee, and 
Liliacee, excepting that the plumule is situated higher up, in consequence of its radi- 
— P" n having become elongated. But in Zunnichellia we find a commencing 
cipe x structure; the radicle has become more enlarged, and a partial ridge is 
gn Br: part round the base of the cotyledon (figs. 4 & 5); but no further | 
: s ervable, as the first leaf of the plumule is directly away from the coty- 
ledon, as in Naias and Potamogeton. | 
m drake ee we find the cotyledon depressed and lying almost horizontally Ja 
té Ei radiele, which forms a shallow ridge surrounding it, so that it appear 
a furrow on its upper surface. This ridge is found to be divided into two parts; 
* The primary radicl : å 
in aa Å cle, as afterwards described, becomes suddenly arrested in its growth, but, as far as it developes, 
