78 



GENETICS IN RELATION TO AGRICULTURE 



2. The Difference in Color of the Cotyledons. The cotyledons of the 

 ripe seeds are either pale yellow, bright yellow, or orange-colored, or 

 they possess a more or less intense green tint. 



3. The Difference in Color of the Seed Coal. This is either white, with 

 which character white flowers are constantly correlated; or it is gray, 

 gray-brown, leather brown, with or without violet spotting, in which 

 case the color of the standards is violet, that of the wings purple, and 

 the stem at the base of the leaves is of a reddish tint. 



4. The Difference in Form of the Ripe Pods. These are either 

 simply inflated, not contracted in places; or they are deeply constricted 

 between the seeds and more or less wrinkled. 



5. The Difference in Color of the Unripe Pods. They are either light 

 to dark green, or vividly yellow, in which coloring the stalks, leaf veins, 

 and calyx participate. 



6. The Difference in Position of the Flowers. They are either axillary, 

 that is distributed along the main stem; or they are terminal, that is 

 bunched at the top of the stem and arranged almost in a false umbel; 

 in this case the upper part of the stem is more or less widened in cross- 

 section. 



7. The Difference in Length of the Stem. The length of the stem is 

 very various in some forms; it is, however, a constant character for 

 each, in so far that healthy plants, grown in the same soil, are only sub- 

 ject to unimportant variations. In the experiments a long axis of 6 to 7 

 feet was always crossed with a short one of % to \% feet. 



The results of segregation in Fz in these seven series of experiments 

 have been summarized from Mendel's paper in Table VII: 



TABLE VII. SUMMARY OF MENDEL'S EXPERIMENTS WITH PEAS 



Mendel observed no transitional forms in these experiments so that 

 the ratios he obtained are based entirely on unprejudiced observations. 

 The ratios in no case differ significantly from the ideal 3:1 ratio. Several 

 investigations have furnished confirmatory evidence as to the correctness 



