stout: pollinations in cichorium intybus 415 



geny of F2 plants of feeble fertility gave an average fertility that 

 showed marked regression to the mean fertility of all self-fertile 

 plants. In these generations, considered as a whole, there was no 

 apparent decrease of fertility due to self-fertilization. The results 

 are quite in line with the exceptional cases of highly self-fertile 

 strains which Darwin discovered in Ipomoea and Mimulus, and 

 which were considered by Darwin as noteworthy exceptions to 

 the general rule that inbreeding decreases fertility. 



Thus far I have not been fully successful in isolating a race 

 solely composed of self-fertile plants. As only two generations of 

 self-fertile progeny have been grown there is the possibility that 

 such races will be isolated. The data obtained indicate clearly 

 that there is no decrease in fertility w^th increased homozygosity 

 and self-fertilization. This fact suggests that a marked degree of 

 similarity or homozygosity is at least not unfavorable to the 

 development and perpetuation of self-fertility. 



Further evidence on this point is to be had from the ancestry 

 of the first self-fertile plants. With the exception of the one 

 plant feebly self-fertile reported in table 7, all the self-fertile 

 plants derived from self -sterile parents are recorded in table 3. 

 Of these (15 in number) all but one are progeny of plants rather 

 distantly related. However, all my Fi generation excepting 8 

 plants of the A X C cross were from crosses of rather widely separ- 

 ated types, hence the results of close crosses between self-sterile 

 plants has not been very fully tested except in the red-leaved 

 Treviso variety, and even here there is evidently much varia- 

 bility. A large majority of the sister plants were self-sterile; 

 and wide crosses did not always give some self-fertile plants, as 

 is seen in the case of the 17 plants from A with Ej, and the 30 

 plants of series 14 (table 3). In respect to the production of 

 self-fertile plants, therefore, no general rule can be made that 

 does not have exceptions. The judgment of cell organization on 

 the basis of the expressed characters of parents, of sister plants, 

 and of offspring may, as is generally recognized in many cases, be 

 quite misleading. 



The range and scope of cross-compatibility and -incompatibility 

 has a bearing on the question of the relation of sterility to cell 

 organization. Cross-pollinations between widely different and 

 unrelated stocks do not always produce seed. The few crosses 



