Tricotylous Races. 456 



outside. I collected the seeds and determined the values 

 in the same way as usual, and obtained the figures which 

 appear in the following summary: 



HEREDITARY VALUES IN ANTIRRHINUM MAJUS. 



Percentage values 

 Dicotyls in the shade 

 Dicotyls in the sun 

 Tricotyls in the shade 

 Tricotyls in the sun 



Number of seed-parents 10, 21, 12 and 24. 



We see that in both cases the proportion of tricotyls 

 was considerably increased by cultivation in the shade. 



The experiments which we have passed in review in 

 this section prove that the proportion of tricotyls in the 

 offspring may be considerably modified by external in- 

 fluences, especially in eversporting varieties, but within 

 certain limits. The differences are such as cannot be 

 neglected in comparative experiments and cultures, and 

 show the importance of carrying out the latter under as 

 constant conditions as possible. In general it must be 

 assumed that a treatment, favorable to the individual 

 flowers and seeds, will increase the production of tri- 

 cotylous seedlings, but the question as to the nature of 

 this relation in the individual cases must, for the present, 

 remain unanswered. 



