The Isolation of Tricotyloiis Intcnncdiate Races. 421 



capacity are rarely found at first. I came across an 

 instance of one only once, at the beginning of my experi- 

 ment with the syncotylous Helianthiis anniius (see the 

 following chapter). If individuals with low hereditary ca- 

 pacities are found, those with mean values can as a rule 

 be easily raised from them, for they are to be regarded 

 simply as minus variants of the race sought for; and 

 will therefore, in conformity with the law of regression, 

 revert to this value even if selection be only suspended 

 (see above, p. 5). Experience shows, and the table al- 

 ready referred to will demonstrate, that one or two gen- 

 erations are, as a rule, sufficient for the attainment of 

 values of 50 to 60%. 



Before I proceed to a detailed description of my ex- 

 periments I will give a few instances to show the course 

 which these experiments in the isolation of tricotylous 

 intermediate races follow. 



The attaimncnt of the mean value. On page 380 I 

 have given, in a small table, the numbers of tricotyls 

 which I found in some samples of seed in the spring of 

 1895. For some of these species these tricotyls were 

 planted out and their seeds saved separately and sown. 

 I obtained values from 12 to 19% in the best individuals 

 (s])ring 1896), and on the rest, as a rule, much fewer. 

 These were regarded as belonging to the half race or as 

 of doubtful significance. The tricotyls from tlic best 

 ])arents were now (1896) planted out, and the hereditary 

 value for each was calculated in the following spring. 

 Below I gi\e a resume of these figures in groups of — 2, 

 v^ — 7, 8 — 129; , with means of 1 — 5 — 10% and so forth, 

 for convenience of comparison, and indicate, f(^r each 

 such reduced value, the number of individuals which 

 exhibited it. 



