CHAPTER XXIII 

 GERMINATION 



305. THE SEED. We have found (259) that by the pro- 

 cess of fertilization a seed is formed. The seed contains a 

 miniature plant or embryo. The embryo usually has three 

 parts which 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. 282), 



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. 

 bean ar r S ,eotyie^ The cotyledons are attached to the caulicle 

 ^"plumule 1 ; 016 /, at /: this point is the first node, and the 

 plumule is at the second node. 



306. 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. 



307. 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. 283. 

 The scar where the seed broke from its funiculus or stalk 



(104) 



