72 FertiUtji in Cichorium intybus 



fully formed, anatonncally perfect, potentially functional, and of simul- 

 taneous development. It is quite evident that the incompatibilities 

 are not due to anatomical incompatibility (structural differences such 

 as hercogamy) or to impotence (degeneration of sex organs or sex cells). 

 Embryo abortion which results from a real gametic incompatibility 

 that develops after fertilization may also be concerned in the decreased 

 seed production and in the poor germinations observed. Such a type of 

 abortion is to be considered as quite distinct from that which more 

 purely involves nutrition. 



As I have already shown (Stout, 1916, 1917) this sort of sexual 

 incompatibility is very general in chicory. It is in evidence in the 

 many instances of cross-sterility and in a very pronounced self-sterility 

 both in wild and in cultivated varieties. 



Self-fertile plants arise, however, among the progeny of self-sterile 

 parents, and in some of my cultures of the variety " Red-leaved Treviso," 

 such self-fertile plants first ajjpeared after three generations of self- 

 sterile parentage. Thus far, in my cultures, the self-fertile plants 

 arising spontaneously have been relatively few in number, and they 

 have exhibited various, grades of self-compatibility as judged by seed 

 production. In the lines of descent grown as offspring of the self-fertile 

 plants, as already reported, the inheritance of self-compatibility was 

 very irregular ; self-incompatibility appeared in all progenies, even when 

 these were offspring of two generations of highly self-fertile plants. 

 I have now to report the results of another generation obtained in 

 1916. 



As is pointed out in my previous papers, the behaviour of known 

 progenies with reference to the development of compatibilities and 

 incompatibilities is of special interest in its bearing on fundamental 

 problems of sexuality and fertilization, especially as they are seen in 

 the bisexual higher plants. 



Material, Methods, and Terminology. 



All of the plants for which data are here presented descended from 

 three self-sterile parents. Two of these parents were of the common 

 unimproved cultivated chicory (Barbe de Capucin) designated in 

 the records as E3 and E22; these were crossed with a wild white- 

 flowered plant designated as A. There are, therefore, two main 

 families which may be referred to according to parentage as the A x E3 

 family and the A x E^2 family (including reciprocals). 



