FAMILIAR SEEDS, STRUCTURE AND GERMINATION 18 
cotyledons remain in the seed, although they are finally 
freed by their own growth bursting the testa. 
8. The Onion Seed.—This is a small black seed, 
irregular in shape, but somewhat pointed at the hilum 
(fig. 8). It contains one cotyledon somewhat curved 
and embedded in endosperm. The plumule is small 
and concealed within the base of the hollow cotyledon. 
Germination proceeds somewhat similarly to that of the 
sunflower. The radicle elongates but then stops grow- 
ing, the usual adventitious roots of the monocotyledon 
being developed at the base of the stem. The lower 
part of the cotyledon elongates, forms a loop and comes 
above ground as the first leaf. The tip remains in the 
seed absorbing the endosperm. Later on a second leaf 
developed from the plumule bursts through the base of 
the cotyledon and comes above ground. 
9. The Date Seed.—The so-called stone of the date 
fruit is the seed (fig. 9). The hard wooden case is the 
testa. A small protuberance on the opposite side of 
the stone to the furrow marks the position of the em- 
bryo. If the seed be cut across transversely at this 
point, a small pointed embryo can be made out sur- 
rounded by a mass of white endosperm. ‘This food 
material is of a hard horny nature owing to the thick- 
ness of the cell walls. If placed in a suitably warm 
and moist situation the seed germinates readily. The 
radicle grows downward, but after a short time branches, 
the main-root system being developed from these 
branches as is usual in monocotyledons. Only the 
stalk and sheath of the cotyledon come above ground. 
The tip remains in the seed as an absorbing organ. 
