256 



MISCELLANEOUS STUDIES 



probably in the incidence of disease, favoring the plants in the west 

 half. The internode data of 1910, however, show a similar tendency. 

 Small genetic differences are suggested, though it would be remarkable 

 if they were so uniformly present in these plants of a single line of a 

 usually selfed species, descendants of parents and a common grand- 

 parent grown under glass. 



If such differences exist in the race, conceivably some combination 

 due to crossing might simulate an early mutation. The evidence as a 

 whole, however, does not favor such an origin for our early type ; it is 

 widely divergent from the Snowflake type, and seems to depend on 

 a single main factor difference from Snowflake. 



TABLE 21 

 Cultures of 1912. Ancestry and parental data. 



* Suspected before testing of belonging to the early type; first parent also 

 tested in 1910. 



b A heterozygote between the crenate-leaved and Snowflake types. 



c Probably open pollinated. 



d All the parents grew in the same house at the same time. 



The essential feature of the supplementary cultures of 1912. since 

 no seed of WL10 remained, was a test of two pairs of early and late 

 progeny of "WL10 (lots 3 and 4, 6 and 7, table 21), in comparison with 

 two control lots one (lot 2) from a known early parent, descended 

 from WG9-C10, and one (lot 5) from a late descendent of WS1. 

 Incidentally, WS1-W 2 16 and WG9-C10-W8 were retested, and the 

 few available seeds of WS1-W,12 were used to test that phenotypically 

 early parent. 



The results are given in tables 22 and 23 and chart 4. The very 

 low individual from WS1-W 2 16 came from a very weak embryo, and 

 should be disregarded; the exceptionally high general range of this 

 lot, which was also visibly behind all others in development, was prob- 



L114] 



