fertility ix cichorium intybus 387 



Discussion and Conclusion 



The sporadic development of self-compatibility giving self-fertility 

 among the progeny of self-sterile lines of descent is in decided evidence 

 in the cultures reported above. No doubt if a larger number of the 

 "red-leaved Treviso" variety had been grown and tested, more than 

 one self-fertile plant would have been found previous to the crop of 

 1 9 16. However, they were not found and the variety was kept in 

 pedigreed cultures by crossing self-sterile plants. 



Self-compatibility is therefore a characteristic that was new in 

 expression, at least to the particular and immediate line of descent 

 involved. A total of loi plants of the 19 16 crop had three generations 

 of ancestry known to be self-sterile; of these 11 plants were self-fertile. 



There is, therefore, much in the occurrence of these plants 

 that suggests discontinuous variation or mutation. However, the 

 fertilities of these self-fertile plants vary. They grade over to 

 complete self-sterility. The variation in the self-fertility of plants 

 grown from self-fertile parents (Stout, 1916, Table 6) is much more 

 continuous and is indicative that the irregular and somewhat dis- 

 continuous variation seen in the intensity of fertilities is only an 

 apparent one due to the few cases observed. 



It is to be noted that there have been scarcely any attempts made 

 to study the progeny of self-sterile plants in species and varieties 

 known to be strongly self-sterile by continued inbreeding in pedigreed 

 lines of descent. Compton (191 2, 191 3) has reported that in Reseda 

 odorata "self-sterile plants when bred inter se throw self-sterile offspring 

 only," but he has not published data regarding the number of such 

 families, the number of plants, or the number of generations tested. 

 East (191 5) has reported that the inter-specific hybrids between 

 Nicotiana forgetiana and N. alata grandifiora have been completely 

 self-sterile for four generations, and that a total of over 500 plants were 

 tested. Data on the behavior of the parent plants, or even of the two 

 parent species, were evidently not obtained, Correns (1912, 1913) 

 was especially interested in the study of cross-incompatibilities and 

 evidently tested the self-fertility of only 13 of the total of 60 sister 

 plants obtained by crossing two self-sterile plants of Cardamine 

 pratense. Of these, however, three plants appear to have been self- 

 fertile. 



In view of the prevalence of self-incompatibilities in many plants 

 of economic importance, such as cabbage, rye, apple, plum, prune. 



