THE SEED AND ITS GERMINATION 5 
seed where the latter was attached to its place of growth in the 
squash. Label this hilum. Note the little hole in the hilum; it is 
the micropyle, seen most plainly in a soaked seed. (If there are two 
depressions on the hilum, the deeper one is the micropyle.) 
Describe the color and texture of the outer coating of the seed. 
With a scalpel or a very sharp knife cut across near the middle a 
seed that has been soaked in water for twenty- 
four hours. Squeeze one of the portions, held 
edgewise between the thumb and finger, in 
such a way as to separate slightly the halves 
into which the contents of the seed is naturally 
divided. Examine with the magnifying glass 
the section thus treated, make a sketch of it, 
and label the shell or covering of the seed and 
the kernel within this. 
Taking another soaked seed, chip away the 
white outer shell called the testa, and observe 
the thin, greenish inner skin (Fig. 1, e), with 
which the kernel of the seed is closely covered.? 
Strip this off and sketch the uncovered ker- 
nel or embryo. Note that at one end it tapers 
to a point. This pointed portion, known as 
the hypocotyl, will develop after the seed sprouts Fig. 1. Lengthwise 
into the stem of the plantlet, like that shown Section of a Squash 
at cin Fig. 9. Seed. (Magnified 
Split the halves of the kernel entirely apart about two aud a 
half times.) 
hypocotyl; cot, coty- 
ledon; e, endosperm ; 
h, hilum; p, plumule; 
_ t, testa. 
from each other, noticing that they are only 
attached for a very little way next tothe hypo- ¢ 
cotyl, and observe the thickness of the halves 
and the slight unevenness of the inner surfaces. 
These halves are called seed-leaves or cotyledons. 
Have ready some seeds which have heen soaked for twenty-four 
hours and then left in a loosely covered jar on damp blotting paper 
at a temperature of 70° or over until they have begun to sprout. 
Split one of these seeds apart, separating the cotyledons, and 
observe, at the junction of these, two very slender pointed objects, 
the rudimentary leaves of the plumule or first bud. 
1 See Sect. 15, 
