562 



WHITE— STUDIES OF INHERITANCE IN PISUM. 



In the F, generation, or from heterozygotes of the same com- 

 position as Fi, the following results have been obtained : 



The first three series of results are less accurate than that of 

 Pellew because the classification of rounds and wrinkleds was not 

 made by examining the starch, hence errors occurred — wrinkleds 

 being sown for round and vice versa. By the starch examination 

 method, there could be no such mistakes, as wrinkleds always have 

 " compound " or much split roundish starch grains. 



Tendrilled zvrinkled X constant round-seeded Acacia segregates 

 (64) gave in F^ the usual results, but in Fo, the round seeds gave 

 502 tendrilled, 270 Acacia, while the wrinkled seeds gave 264 ten- 

 drilled, o Acacia. 



Pellew tested out other pairs of characters with tendrils and 

 Acacias to see if there was any coupling, but none was found. 

 Among these pairs tested were tallness and dwarfness, yellow and 

 green cotyledons, purple and white flowers, glaucous and emerald 

 foliage and fasciated and normal stems. 



Interpretation, 



The factor (R) for roundness of seed, etc., and its absence (r) 

 for wrinkled seed, etc., have already been considered. Tendrilled 

 and non-tendrilled plants (Acacia) are due to the respective pres- 

 ence and absence of the factor Tl. The peculiar ratios obtained as 

 regards both sets of factors show that partial linkage or coupling 

 exists between R and Tl on the one hand and r and tl on the other. 

 The interpretation of the manner in which this partial coupling is 

 brought about is too extended to consider here. Suffice to say that 

 Bateson (3.5) and his students explain it by somatic segregation and 

 the increased rapidity of growth of the germ cell area which is to 

 give rise to the large classes, as compared to that which gives rise to 



