3YO PLANT STUDIES 
from the seed. Formerly it was called either caulicle or 
radicle. In Dicotyledons the stem-tip between the coty- 
ledons often organizes the rudiments of subsequent leaves, 
forming a little bud which is called the plumule. 
Embryos differ much as to completeness of their devel- 
opment within the seed. In some plants, especially those 
which are parasitic or saprophytic, the embryo is merely a 
small mass of cells, without any organization of root, stem, 
or leaf. In many cases the embryo becomes highly devel- 
oped, the endosperm being used up and the cotyledons 
stuffed with food material, the plumule containing several 
well-organized young leaves, and the embryo completely 
filling the seed cavity. The common bean is a good illus- 
tration of this last case, the whole seed within the integu- 
ment consisting of the two large, fleshy cotyledons, between 
which lie the hypocotyl and a plumule of several leaves. 
245. The seed. As in Gymnosperms, while the processes 
above described are taking place within the ovule, the in- 
tegument or integuments are becoming transformed into 
the testa (Fig. 330). When this hard coat is fully devel- 
FIG. 330. The two figures to the left are seeds of violet, one showing the black, hard 
testa, the other being sectioned and showing testa, endosperm, and imbedded 
embryo ; the figure to the right is a section of a pepper fruit (Piper), showing 
modified ovary wall (pc\ seed testa (sc), nucellus tissue (p), endosperm (en), and 
embryo (em). After ATKINSON. 
oped, the activities within cease, and the whole structure 
passes into that condition of suspended animation which is 
so little understood, and which may continue for a long 
time. 
