4l8 BOTANY OF CROP PLANTS 



thin; endosperm is wanting; the stored food is within the two 

 cotyledons. The cotyledons remain underground during 

 germination {hypogean germination), as in all cereals. This 

 type of germination is different from that in the bean and 

 squash, for example, in which the two cotyledons are raised 

 above ground, and for a time are food-making organs. 

 This sort of germination is called epigean. 



Types of Peas. — There are but two well-recognized types 

 of Pisum: Garden peas and field peas. These are briefly 

 distinguished as follows: 



Flowers white; seeds globular, uniformly yellowish, white or bluish green; 

 leaf axils green, unpigmented; comparatively tender Pisum sativum 

 (garden pea). 



Flowers colored, usually purplish, red or lavender; seeds angular, gray- 

 brown, gray-green, gray-yellow or gray speckled with fine spots of various 

 colors; leaf axils pigmented; comparatively hardy Pisum salivuvi (field 

 pea). 



Garden Peas. — The common garden pea can be divided 

 into two groups: Shelling peas, and edible-podded or sugar 

 peas. In the former, the pod is lined on the inside by a thin, 

 hard membrane (endocarp) which at maturity causes it to 

 split open. In the edible-podded or sugar peas, this mem- 

 brane does not become dry and twisted at maturity, and 

 the pods remain soft and tender. 



Shelling Peas. — Vilmorin classifies the varieties of common 

 shelling peas into two groups: Round or smooth-seeded, and 

 •wrinkled-seeded. Each of these is divided into (i) tall climb- 

 ing, (2) half-dwarf, and (3) dwarf varieties, and each of the 

 latter three groups into white-seeded and green-seeded sorts. 

 The sugar peas occur in both tall, half -dwarf, and dwarf 

 forms. 



Period of Maturing. — As a general rule, the earliest sorts 

 of peas have smooth, round seeds, while the late sorts have 



