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 ' t 

 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 Partg of 



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



first node, and the plumule is at the second ,a, iiu'muie; f, 



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) 



