96 University of California Publications in Agricultural Sciences [Vol. 4 



The differentiation of the earlv race is verv marked : with the 

 singles, in fact, the later cultures indicate no case of overlapping in 

 the 1908 cultures, in either character, between extracted pure Snow- 

 flake and pure or heterozygous early. The total sterility of the doubles 

 necessarily leaves their constitution somewhat in doubt. 



The cultures of 1908 so far suggest that WG9-C10 was a mutant. 

 To be reasonably certain, however, we must have further evidenc(; 

 (1) on the fact and mode of inheritance of the supposed new type, 

 and (2) on the possibility that either WG9 or some other plant of 

 the cultures of 1906 brought the character into the cultures. We shall 

 now consider somewhat extensive evidence bearing on these points, 

 concluding with a special test of the possibility of vicinism. 



When I last saw the warm-house plants of 1906, three were known 

 to be singles, and all but two of the rest were recorded as certainly 

 or probably doubles. Seed was secured from these three singles only, 

 and presumably no other singles occurred in the house. Since this 

 seed was all from unguarded flowers, we must consider the possibility 

 that WSl or WLIO, the other warm-house singles, brought the early 

 factor into the cultures. It is also barely possible that pollen was 

 brought to WG9 from some plant not in this greenhouse. 



These two parents were tested in .supplementary cultures, in house 

 C in 1907, and in house W in 1908. The 1907 progeny averaged 

 slightly earlier than those of other parents, but this may have been 

 due to their position, which was much nearer a partition separating 

 the house^" from a warm greenhouse. Unfortunately the internodes 

 were not recorded. 



In the 1908 cultures these lots were potted two days later than 

 most of the other lots and one day later than the AVG9 lot, and for 

 some unlmown reason the WLIO lot wilted badly for some days. The 

 parents in question gave singles (16 and 11 plants respectively) which 

 when compared with progeny of CG2 and WG9 (23 and 15) might 

 suggest that the parents were heterozygous for the early type. The 

 results with the similar numbers of doubles decidedly disagree with 

 these, and suggest that cultural accidents produced the differences ; 

 the WSl lot was not exceptional, while all the WLIO progeny were 

 grouped near the lower end of the range of the other lots. In view of 

 all the facts, the data hardly deserve tabular presentation, but they 

 raise a question requiring further study; a later test is reported below. 



1" A temporary substitute for the regular house C. 



