stout: pollinations in CICHORIUM INTYBUS 393 



Of the 7 tested as pollen-parents with K22, 3 showed cross- 

 fertility. 



The plant {E22 X A) no. i was sterile with pollen of two sister 

 plants and feebly fertile to one; the plant {E22 X A) no. j was 

 sterile to pollen of 4 sister plants. The parent plant A was tested 

 with pollen of 5 of the {E22 X A) plants, with 4 of which it w^as 

 fertile. 



As far as tested the hybrids of this series showed strong cross- 

 sterility, as out of 28 combinations only 5 were fertile. On the 

 other hand there was rather marked fertility when pollen of these 

 plants was used on the parent A. 



Eleven of the crosses given in table 13 involve pollen from a 

 self-fertile plant with a seed-parent that is self-sterile: 6 of these 

 crosses were fertile. The pollen of the self- fertile plant (A X 

 E22) no. 4 was sterile to the parent E22 and to a sister plant 

 (A X E22) no. 10, but was highly fertile to the parent A . These 

 results agree with those of table 12 in showing that the self-fertile 

 plants are not cross-fertile as pollen-parents with all of their 

 sister plants, and that when fertile there may be considerable 

 variation in the degree of fertility. These facts are suggestive 

 that cross-sterility from physiological incompatibility may exist 

 between plants of the same species that are self-fertile. The 

 difficulty of making emasculations or depollinations in chicory 

 necessary to controlled cross-pollination between self-fertile plants 

 had thus far deterred me from making this test. 



A summary of the cases of back crosses given in tables 9, 11, 

 12, and 13 shows that plant A was crossed as a seed-parent with 

 46 of its progeny and that in 25 cases there was fertility. The 

 total of all back crosses of offspring on a known parent is 69, of 

 which 35 were fertile and 34 sterile. The number agrees more 

 closely than do the results of Correns with his theoretical ratio for 

 such a cross in Cardamine. The range of variation in the actual 

 fertility, however, is so great in both cases that the grouping of 

 all offspring into two classes with reference to cross-fertility with 

 a parent is of little significance, and in addition the results ob- 

 tained in the pedigreed self-fertile strains of chicory show that 

 the conception of line stuffs is untenable. 



Results of cross-pollinations involving the variety ''improved red- 

 leaved Treviso.'' — Data have already been presented (table 7) for 



