[Reprinted from the American Journal of Botany, 4: 375-395, July, 1917.] 



FERTILITY IN CICHORIUM INTYBUS: THE SPORADIC 



OCCURRENCE OF SELF-FERTILE PLANTS AMONG 



THE PROGENY OF SELF-STERILE PLANTS 



A. B, Stout 



The writer (1916) has already presented the evidence that the 

 very prevalent self-sterility (and cross-sterility as well) in chicory can 

 be ascribed to a physiological incompatibility operating between sex 

 organs or sex cells that are fully formed, anatomically perfect, poten- 

 tially functional and of simultaneous development. It was noted that 

 this type of sexual sterility is sharply to be distinguished from sterility 

 due to anatomical incompatibility (more or less purely structural dif- 

 ferences and adaptations such as hercogamy), impotence (failure to 

 produce gametes) or embryo abortion (death of egg after fertilization 

 or death of young embryo). I also at that time discussed and sum- 

 marized the literature bearing on such phenomena. 



From my studies made in 1912 and 1913, it appears (Stout 1916, 

 p. 365-366) that self-sterility is the rule in chicory. Three plants (des- 

 ignated A, B, and C) of wild stock were found to be self-sterile, as 

 were 52 plants grown from the open fertilized seed of these plants, 

 and all plants tested of ten cultivated varieties were self-sterile. In 

 one variety (Barbe de Capucin), 29 plants of one planting and 5 of 

 another were tested, and of other varieties about five plants of each 

 were tested. The total of about 135 plants from these various sources 

 were self-sterile. 



However, in the pedigreed cultures grown in 1913, a few plants 

 exhibiting varying degrees of self-fertility appeared quite sporadically 

 among the Fi progeny of various crosses between self-sterile plants. 

 Of the 75 plants derived by crossing plant A with plant E22 (of the 

 variety Barbe de Capucin), only eight were self-fertile. Of 21 plants, 



375 



