CHAP. II. 
SEED. 
209 
With regard to the quartine and quintine, one of them is 
occasionally present in the form of a fleshy sac that is inter- 
posed between the albumen and the ovule, and envelopes the 
latter. It is what was called the vitellus by Gsertner, and 
what Richard, by a singular prejudice, considered a dilatation 
of the radicle of the embryo : to his macropodal form of which 
he referred the embryo of such plants. Instances of this are 
found in Nymphaea and its allies, and also in Scitamineae, 
peppers, and Saururus. Brown, who first ascertained the 
fact, considers this sac to be always of the same nature and 
origin, and as the vesicula colliquamenti or amnios of Malpighi. 
The end by which the seed is attached to the placenta is 
called the hilum or umbilicus (Plate VI. fig. 5. c, 17. ^, 11. c, 
&c.) ; it is frequently of a different colour from the rest of the 
seed, not uncommonly being black. In plants with small 
seeds it is exceedingly minute, and recognised with difficulty ; 
but in some it is so large as to occupy fully a third part of 
the whole surface of the seed, as in the horse-chestnut, Sa- 
poteae, and others. Seeds of this kind have been called 
nauca by Gaertner. In grasses the hilum is indicated by a 
brownish spot situated on the face of the seed, and is called 
by Richard spilus. The centre of the hilum, through which 
the nourishing vessels pass, is called by Turpin the omphalo- 
dium. Sometimes the testa is enlarged in the form of irregu- 
lar lumps or protuberances about the umbilicus; these are 
called strophiolcB or carunculce ; and the umbilicus, round 
which they are situated, is said to be strophiolate or carun- 
culate. Mirbel has ascertained that in Euphorbia Lathyris 
the strophiole is the fungous foramen of the primine ; and it is 
probable that such is often the origin of this tubercle : but at 
present we know little general upon the subject. 
The foramen in the ripe seed constitutes what is called the 
micropyle : it is always opposite the radicle of the embryo ; 
the position of which is, therefore, to be determined without 
dissection of the seed, by an inspection of the micropyle, — 
often a practical convenience. 
In some seeds, as the asparagus, Commelina, and others 
(fig, 185.), there is a small callosity at a short distance from the 
hilum : this callosity gives way like a little lid at the time of 
p 
