SEEDS AND GERMINATION 21 



bark-bearing trees and bushes (except conifers;, and most 

 of the herbs of temperate climates except the grasses, 

 sedges, rushes, lily tribes, and orchids. The flower-parts 

 are usually in fives or multiples of five, the leaves mostly 

 netted-veined, the bark or rind distinct, and the stem often 

 bearing a pith at the center. The monocotyledons usually 

 have the flower-parts in threes or multiples of three, the 

 leaves long and parallel-veined, the bark not separable, 

 and the stem without a central pith. 



Every seed is provided with food to support the germinat- 

 ing plant. Commonly this food is starch. The food may 

 be stored in the cotyledons, as in bean, pea, squash ; or out- 

 side the cotyledons, as in castor bean, pine, Indian corn. 

 When the food is outside or around the embryo, it is 

 usually called endosperm. 



Seed-coats ; Markings on Seed. The embryo and en- 

 dosperm 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 FIG. 16. EXTER- 

 the pollen-tube entered the forming ovule NAL PAR-IS OF 

 and through which the caulicle breaks in 

 germination. The micropyle is shown at M in Fig. 16. 

 The scar where the seed broke from its funiculus (or stalk 

 that attached it to its pod) is named the hilum. It occu- 

 pies a third of the length of the bean" in Fig. 16. The 

 hilum and micropyle are always present in seeds, but they 

 are not always close together. In many cases it is difficult 

 to identify the micropyle in the dormant seed, but its loca- 

 tion is at once shown by the protruding caulicle as germi- 

 nation begins. Opposite the micropyle in the bean (at the 

 other end of the hilum) is an elevation known as the raphe. 



