116 Self- Incompatibility in Hermaphrodite Plants 



fertility. In the I^, Series 12-11 was more self- fertile both as to pro- 

 portion of plants and range of self-fertilities. In the /g. considering 

 each family as a whole, there was no difference in the proportion of 

 plants, but the ranges were higher for one series of the family 12-11- . 

 Some irregularities are apparent in which the behaviour of offspring 

 is not directly to be gauged by the degree of self-fertility of a parent. 

 In the 7i of family 10-8- one series {10-8-173) gave a ratio of 2 self- 

 sterile to 1 self-fertile while in the other series this ratio was reversed ; 

 the grades of s'elf- fertility for the three immediate parents were almost 

 identical and they all had the same ancestry preceding. In the I^ of 

 the family 12-11-, the two series were obtained from parents of almost 

 identical self-fertility ; one of these {12-11-1^.9) was of decidedly feeble 

 self-fertility in comparison with the other {12-11-16). 



IV. Vegetative vigour and impotence in self-fertilized lines in the 

 variety red-leaved Treviso of Cichorium Intyhus. 



The various grades of seed development and embryo abortion in 

 plants feebly self-compatible suggest strongly that individuals of 

 various grades of vegetative growth may arise through various grades 

 of compatibility in the fertilizations. The physiological basis for 

 degeneracy in individuals or races may thus be sought, in part at least, 

 in the comparative weak compatibility of the elements which unite in 

 fertilization. That this is the case is also suggested by the evidence 

 that inbreeding and continued self-fertilization is not of itself injurious. 



The self-fertilized lines of descent in this variety of chicory were 

 derived from a race that was kept in culture for three years by cross- 

 fertilization of rather closely related plants. Undoubtedly the variety 

 had previously been maintained largely by crossing, and it is a salad 

 chicory that has been developed and maintained by selection for 

 vigorous vegetative growth. Under such treatment there has been a 

 constant selection of the offspring of highly compatible fertilizations and 

 an elimination of weak individuals which in my culture have been given 

 a chance for their complete development. 



In the cross-fertilized stock of the first three years of culture there 

 were occasional plants that exhibited signs of degeneracy. The leaves 

 and branches were few and poorly developed, flower heads did not open 

 fully, corollas were crumpled, and many anthers were dark coloured, 

 contained few well-developed pollen grains and often did not dehisce. 

 Such plants produced few seed to open cross-pollination. During the 



