CHAPTER XXV 



GERMINATION 



332. The Seed. — We have found (276) that as a result 

 of fertilization a seed is formed. The seed contains a minia- 

 ture plant or embryo. The embryo usually has three parts 

 that have received names: the little stemlet or caulicle; 

 the seed-leaf or cotyledon (usually 1 or 2); the bud or plumule 

 lying between or above the cotyledons. These parts are well 

 seen in the common bean (Fig. 308), particularly when the 

 seed has been soaked for a few hours. 

 One of the large cotyledons — comprising half 

 of the bean — is shown at r. The caulicle is 

 at c. The plumule is at a. The cotyledons are 308 Part9 of ° the 

 attached to the caulicle at /: this point is the bean - r < cotyie- 

 first node, and the plumule is at the second a, plumule; /, 

 node. firstnode - 



333. Every seed is provided with food, to support the 

 germinating plant. Commonly this food is starch. The 

 food may be stored in the cotyledons, as in bean, pea, squash ; 

 or outside the cotyledons, as in castor bean, pine, Indian 

 corn. When the food is around the embryo, it is usually 

 called endosperm. 



334. The embryo and endosperm are inclosed within a 

 covering made of two or more layers and known as the seed- 

 coats. Over the point of the caulicle is a minute hole or a 

 thin place in the coats known as the micropyle. This is 

 the point at which the pollen-tube entered the forming 

 ovule and through which the caulicle breaks in germination. 

 The micropyle is shown at m in Fig. 309. The scar where 

 the seed broke from its funiculus or stalk is the hilum. It 



(171) 



