402 Tricotylous Races. 



sisted of the 20 best tricotyls only, and 16 of these ripened 

 their seeds. In this generation, however, there was a 

 considerable step back, for the individual parents varied 

 between 0.5% and 3.7% ; and one parent had not a single 

 aberrant form amongst 200 seedlings. The mean was 

 1.8%. The seeds of the five best plants were again sown 

 and 1000 seedlings from each examined. The values 

 were now 2.6 — 2.8 — 3.2 — 3.2 and 3.6%. In the following 

 years I endeavored to determine the cause of this re- 

 turn by a series of collateral experiments, but without 

 success. The variability of the hereditary value in such 

 races obviously depends in great part on causes which 

 we do not yet understand. 



I now planted out the tricotylous offspring of two 

 plants with 3.2 and 3.6%, but in two separate groups 

 in order to be able to confine the selection to the offspring 

 of one of them later, if desired. These cultures consisted 

 of 12 and 13 tricotyls, no essential difference between 

 them being manifested. The values calculated from the 

 batches of 300 seedlings from each seed-parent were : 



SEED- VALUES CALCULATED FROM THE OFFSPRING 



PARENT (Spring, 1896) 



with 3.2 % 1.3 1.7 1.7 2.0 2.3 2.3 2.7 2.7 2.7 3.0 4.0 5.5 

 with 3.6% 0.7 0.7 1.0 1.3 1.7 2.0 2.7 2.7 3.0 3.0 3.7 4.7 5.3 



The mean for both cases was therefore about 2.5% 

 (actually 2.5% and 2.7% respectively). This experi- 

 ment proves how little effect an enlargement of the ex- 

 tent of the cultures has in such an experiment in selection, 

 for if I had only dealt with the offspring of one of the 

 two parents, the result would obviously not have been 

 essentially different. 



In the summer of 1896 I did not go on w^ith this cul- 

 ture, but tried to find out whether by planting out a con- 



