The Isolation of Tricotylous Iiitciiucdiatc Races. 441 



were already present in the (^-iginal sanii)le of seed, ov 

 l)ecaiise between the interme(hate and the half races hy- 

 brids were met with, by the snbsequent segregation of 

 wliich the race w^as produced. 



In the first experiments the isolation of the tricotyl- 

 ous intermediate race took from three to four genera- 

 tions. Later when I started tlie experiments on a larger 

 scale, the number was reduced to two years. Further 

 selection brought it up, in one year as a rule, to 70 — 

 80% and sometimes even to 90%, either immediately 

 in the course of another year, or after two generations. 

 Unfavorable conditions of life led to exceptions, or even 

 to retrogression ; but only Helichrysuin and Silcne ex- 

 hibited this feature. Cannabis, Mercurial is and Antir- 

 rhinum maintained a value of 80 — 90% under continued 

 selection, and it is quite probable that even 100% might 

 have been attained in occasional individuals. The mean 

 figures of the wdiole group correspond, as a rule, to these 

 maximum values. They maintained themselves at about 

 55%, but are liable to be increased by selection or dimin- 

 ished by unfavorable conditions. 



Lastlv, it should be noted that the ni>ures for these 

 intermediate races are so far removed from those of the 

 half races (p. 392), that all suspicion as to the possible 

 effect of occasional errors in the choice of the samples 

 is excluded ; in other words, that hereditary z'aines from 

 1 to 5% or ez'cn of 5 to 20 9^ , // they are maintained in 

 spite of selection, may he regarded as characteristic of 

 half races, whilst values of 40 to 60% . idioi found in 

 separate crops, may be taken to indicate the presence of 

 intermediate races. 



A\nien an intermediate race is isolated from an orig- 

 inal sample of seed, it is separated from the half race 



