NATURE AND GENERAL CHARACTERS OF THE SEED. 333 
2. THE SEED. 
NATURE AND GENFRAL CHARACTERS OF THE SEED AS COM- 
PARED WITH THE OvuLE.—The seed is the fertilised ovule. 
Like the ovule, it is either attached directly to the placenta, in 
which case it is described as sessile; or by means of a stalk, 
called the funiculus or funicle (figs. 668, f, and 748, f), when it is 
said to be stalked ; its point of attachment 
is also termed the hilum. The position 
of this hilum may be commonly seen on 
seeds which have separated from the funi- 
culus or placenta, by the presence of a scar, 
or in a difference of colour to the sur- 
rounding integument. The hilum varies 
muchin size, being sometimes very minute, 
while in other cases it extends for some 
distance over the surface of the outer coat 
of the seed, as in the Horsechestnut and 
Calabar Bean. The centre of the hilum, 
Fic. 748. 
” 
I 
te! | 
Ee” Pap pb 
Fig. 748. The seed of a 
Pea, with its integu- 
ments removed on one 
through which the nourishing vessels pass, side. p/. Placenta. f. 
has been called the omphalodium. The 
hilum, as in the ovule, indicates the base 
of the seed, while the apex is represented 
by the chalaza. This chalaza (fig. 748, ch) 
is generally more evident in the seed than 
in the ovule, and is frequently of a differ- 
ent colour to the other parts. It is well 
seen in the Orange, and commonly in all 
anatropous seeds, in which case also the 
Funiculus. 7ap. Raphe. 
ch. Chalaza. m. Micro- 
pyle. te. Testa or epi- 
sperm. e. Endopleura 
or tegmen. The part 
within the endopleura 
is commonly called the 
nuc'eus of the seed, and 
is formed of cotyle- 
dons, ce, gemmule or 
plumule, g, radicle, 7, 
and ¢ stalk or tigellum 
between the plumu'te 
raphe may be generally noticed forming and radicle. 
a projection on the face of the seed. 
The micropyle also, although smaller and less distinct than 
in the ovule, owing to a contraction of the surrounding parts, 
may be frequently observed on the seed (fig. 748, m); its 
detection is of some practical importance, as the radicle, r, 
of the embryo, with a few exceptions, is directed towards 
it. Itshould be noticed that while the micropyle constitutes 
the organic apex of the ovule, the chalaza indicates that of 
the seed. 
The terms orthotropous, campylotropous, anatropous, &ce., 
are applied to seeds in the same sense as to ovules ; consequently 
the hilum, chalaza, and micropyle have the same relations to 
one another in the seed as in the ovule. Thus the hilum and 
chalaza are contiguous to each other in an orthotropous seed, 
and the micropyle is removed to the opposite end ; in a campy- 
lotropous seed the hilum and chalaza are also near to each 
other, and the micropyle is brought round so as to approach 
the hilum ; in an anatropous seed the chalaza is removed from 
