644 PHARMACEUTICAL BOTANY 
Mendel experimented with the hereditary characters of 
various kinds of garden peas because these were the best materials 
he could find to test out his ideas and obtain light on the prob- 
lems of heredity and variation in which he was so keenly 
interested. Hestudied seven pairs of constant differentiating char- 
acters in the peas he worked with, namely, tall vs. dwarf stems; 
round (smooth) vs. wrinkled (angular) seeds; yellow vs. green 
seeds; colored flowers and seed coats vs. white flowers and seed 
coats; parchmented vs. non- 
parchmented pods; green vs. 
bright canary yellow, unripe 
| pods; and normal round stems 
| with axillary flowers vs. fasci- 
ated (flattened) stems with ter- 
j} minal or umbellate flowers. 
The members of such pairs of 
contrasting (alternative) char- 
| acters were called allelomorphs 
by Bateson. Each member of 
two different strains of plants 
which can be crossed, as for 
example, a tall stemmed pea 
with a dwarf stemmed pea, is 
Fic. 483.—Gregor Johann Mendel at the -said to be allelomorphic to the 
ee other. : 
Mendel’s Laws embody the following principles: 
1. Tue Princiete or Unrr CHaracters.—The inheritance of 
THE PURITY OF THE GERM CeLis (GaMETES).—Every germ cell is 
pure with respect to any given unit character. In the germ cells _ 
