STRUCTURE AND GERMINATION OF SEEDS 21 



Remove a seed (Fig. 7, 1). Notice that it is flattened and 

 oval ; one edge is convex and the other slightly concave ; 

 it is covered on the outside by a thick, tough, light-brown 

 skin the testa (6 1) ; and when the seed-stalk or funicle (fu) 

 is removed, a scar or hilum (2 h) is left, indicating the point 

 of attachment. Compare this seed with a dry one (3) 

 as supplied by the seedsman, and note the darker wrinkled 

 skin of the latter and the prominent dark-brown scar. 

 Evidently such a seed has lost much water. If one of 

 these seeds is soaked in water, a marked change occurs. 

 In six or seven hours the skin becomes more wrinkled 

 (4), then the seed swells so much that the skin is 

 tightly stretched, and if it be squeezed laterally, a little 

 drop of water will be seen to ooze out from a small hole 

 the micropyle (Gr. mikros = small, Pyle = gate) at one 

 end of the scar (2 and 5 m). Wipe off the water and 

 repeat the experiment. As we shall see later, this hole 

 represents the micropyle of the ovule, through which the 

 pollen-tube entered when fertilization took place. 



Remove the skin (6 t) from the seed. Note its thick- 

 ness ; examine the inner surface of the coat covering the 

 concave edge ; find the little pocket and determine its use 

 (6 and 7 r.p). The structure enclosed by the skin consists 

 of two large fleshy lobes the seed-leaves or cotyledons 

 (8 and 9 c), and between these is a bluntly-pointed struc- 

 ture the radicle (8 ra), the tip being directed towards 

 the micropyle. The pocket in which it rested is called 

 the radicle pocket. 



Separate the two cotyledons and look for the young, 

 curved shoot, bearing tiny leaves at its tip. This is the 

 plumule (8 pi). Between the plumule and the radicle 

 thick stalks are given off to the cotyledons. These struc- 

 tures the two cotyledons, radicle, and plumule form 

 a young, dormant plantlet called the embryo. 



Compare the pod and seeds of the Garden Pea or the 



