CHAr. II. 
EMBRYO. 
253 
embryo is that of Araceae and their allies, in which the plu- 
mule is not so intimately combined with the embryo as to be 
undistinguishable, but is indicated externally by a little slit 
above the base (Plate VI. fig. 6. b e), within which it lies 
until called into developement by germination. 
The exceptions to what has been now described ought, like 
those of dicotyledons, rather to be called remarkable modifi- 
cations. Much stress has been laid upon them by several 
writers, who have thought it requisite to give particular 
names to their parts. To me, however, it appears far more 
advisable to explain their analogies without the unnecessary 
creation of new and bad names. In Graminaceae (Plate VI. 
fig. 4.) the embryo consists of a lenticular body lying on the 
outside of the base of the albumen on one side, and covered 
on its inner face by that body, and on its outer face by the 
testa : if viewed on the face next the testa, a slit will be ob- 
served of the same nature as that in the side of the embryo 
of Araceae; within this cleft a small conical projection is 
discovered, pointing towards the apex of the seed. If the 
embryo be then divided vertically through the conical pro- 
jection, it will be seen that the latter (c) is a sheath including 
other little scales resembling the rudiments of leaves; that 
that part of the embryo which lies next the albumen (c?), and 
above the conical body, is solid ; and that the lower extre- 
mity of the embryo (e) contains within it the indication of an 
internal radicle, as in other monocotyledons. In this embryo 
it is to be understood that the conical projection is the plu- 
mule ; that part of the embryo lying between it and the al- 
bumen, a single scutelliform cotyledon; and the lower point 
of the embryo, the radicle. In Wheat there is a second small 
cotyledon on the outside of the embryo, inserted a little lower 
down than the scutelliform cotyledon. This last is called 
scutellum by Gaertner, who thought it of the nature of vitellus. 
Richard considered the scutelliform cotyledon a particular 
modification of the radicle, and called it hypoblastus ; the plu- 
mule a form of cotyledon, or blastus ; the anterior occasional 
cotyledon a peculiar appendage, or epiblastus ; and the radicle 
a protuberance of the caulicule, or radiculoda. He, further, 
in reference to this opinion, termed embryos of this descrip- 
