104 Sdf- Incompatibility in Hermaphrodite Plants 



branches which bloom later than the main ones usually omit certain of 

 the earlier stages exhibited by the latter. The evidence seems con- 

 clusive that when compatible cross-pollination is made there is production 

 of fruit and seed in any stage except (1) and (5). The highest degree 

 of self-compatibility appears to develop during the mid-season of bloom. 

 During the latter part of the period of bloom (designated above as 

 period 4) there is usually a poor development of pods and these may 

 contain only partly formed seeds in which embryo abortion has taken 

 place. This is evidently due to the rapid decline and death of the entire 

 plant. 



Raphanus sativus. 



It can here be reported that some cultivated varieties of this species 

 are decidedly self-incompatible. Nearly 50 plants of three varieties 

 grown to maturity in a greenhouse have completely failed to produce 

 pods to self-pollination. Of plants tested thus far only one has shown 

 signs of self-fertility. It was grown in the field, bloomed from June 22 

 to July 13, and produced 223 flowers many of which were selfed by hand. 

 Six small pods were produced, each containing from 1 to 2 seeds. All 

 these were for flowers which opened during the mid-season of bloom. 

 Further studies with varieties of the radish and also of the Chinese 

 cabbage are in progress. 



Lythrum Salicaria. 



The marked sterility of this trimorphic species to self, to intra-form, 

 and to inter-form illegitimate pollinations was noted by Darwin (1865). 

 His experiments revealed, however, that self-fertility is somewhat in 

 evidence especially in the mid-styled plants. 



My own experiments with this species have thus far been confined 

 chiefly to the growing of plants in isolation for the observation of seed 

 production when subjected to free self-pollination by insects. The 

 results thus far obtained show (1) that short-styled plants set very few 

 pods ; (2) that long-styled plants are feebly self-fertile and that (3) mid- 

 styled plants are often decidedly self-fertile. One mid-styled plant 

 grown under constant observation in my own garden has shown a decided 

 increase in fertility at the end of the period of bloom. All other plants 

 tested have shown quite a uniform degree of self-compatibility through- 

 out the entire period of bloom. 



End-season self- fertility in this species has to date been observed 

 in only one plant. This condition seems to develop as an individual 



