LEGUMINOS^ 421 



Peas and Mendelism. — Gregor Mendel's famous experiments in plant 

 hybridization were carried on with the common garden pea. He discovered 

 certain laws in the behavior of his hybrids, and these are now famed as 

 Mendel's Laws. He selected a number of differentiating (paired) characters 

 and observed their behavior when crossed with each other. In the brief 

 summary, here of his work, a number of characters of the genus Pisum are 

 brought out: 



1. Round or roundish form of seed is dominant over angular or wrinkled 

 seed. That is, when a plant bearing roundish seeds is crossed with one bear- 

 ing angular or wrinkled seeds, the hybrid offspring bears seeds all of which are 

 roundish. 



2. Yellow color of cotyledons is dominant over green color of cotyledons. 



3. Gray seed coats are dominant over white seed coats. 



4. Inflated seed pods are dominant over pods constricted between the seeds. 



5. Green color of unripe pods is dominant over yellow color of unripe pods. 

 . 6. Distribution of flowers in leaf axils is dominant over their distribution on 



the ends of stems. 



7. Tall stem is dominant over short stem. 



Uses. — Peas in the green state are one of the most common 

 vegetables. They are also canned in large quantities. Field 

 peas are being grown as a companion crop, soiling crop, 

 green manure, and as a food for hogs, sheep, horses and 

 cattle. It is the practice in many places to pasture live 

 stock, particularly hogs and sheep, on field peas. 



PHASEOLUS (Bean) 



Description. — Representatives of this genus are annual or 

 perennial herbs or vines with pinnately three-foliate, rarely 

 one-foliate, leaves. The flowers occur in axillary racemes; 

 they vary in color: white, yellow, red, or purple. The calyx 

 is five-toothed or five-lobed, the two upper teeth or lobes 

 being either united or free. The standard of the corolla is 

 often recurved or somewhat contorted; the wings equal or 

 exceed the standard, while the keel is characteristically spirally 

 coiled (Fig. 176, A). The stamens are diadelphous (nine 

 and one). The ovary has a style longitudinally bearded,. and 



