88 Self-Incompatihility in Hermaphrodite Plants 



Certain lines of descent from self- fertile parentage did not breed 

 true. For example one parent was 4*4 °/„ self-fertile. The self-fertilities 

 of the four progeny were 43-1 °/„, I'l 7,, 1-6 7„ and 0-0 7„. In the next 

 generation three offspring of the plant 43*1 °l^ self-fertile were all self- 

 fertile (15-5 7„, 20-0 7„ and 11-8 7J, and the three offspring of the plant 

 1-1 7, self-fertile were 0-7 7,, 0*5 7, and 0-0 °/^ self-fertile. 



Heribert-Nilsson, none the less, concludes that these feebly self- 

 fertile plants are really heterozygotes. When Heribert-Nilsson states 

 that self-fertility is a recessive character in a simple mono-hybrid 

 relationship with self-sterility, and that self-fertility segregates as a 

 unit in heredity and is immediately constant, he contradicts his own 

 data. His assumption of this simple Mendelian analysis is obviously on 

 a priori grounds. The variations in degree of self-fertility in evidence 

 are so great and the number of plants grown is so small that there is 

 certainly no positive evidence that the relative physiological conditions 

 of the sex organs are determined by line stuffs of specific and fixed 

 hereditary values. Obviously the true conclusion is that rye plants are 

 more or less heterozygous as to self-futility, which is merely another way 

 of saying that they are fluctuatingly variable in their self-compatibility. 



Heribert-Nilsson finds evidences of degeneration in self-fertilized 

 lines, both in the quality and viability of se6d, and in the vegetative 

 vigour of the offspring, but he questions whether this is due to the 

 immediate physiological effects of selfing, or to an increase in homo- 

 zygosity. It should be noted that he gives rather meagre data for 

 the two series of sister plants of the I^ which were most vigorous in 

 vegetative growth. One series of five plants is described as " kraftig " 

 but the self-fertility of its members was evidently not determined. Of 

 another series of nine plants of which it is stated " die Mehrzahl recht 

 kraftig" fertility was determined for only three, and these were all 

 self-fertile (25-8 7,^, 28-6 7„, 14-6 7 J. It is, however, stated thaf all 

 seeds of the li were poorly developed, but it appears that the conditions 

 of artificial isolation (glass tubes plugged with cotton) led to vigorous 

 growth of fungi which covered the seeds as they were developing, and 

 this may have been the real cause of the poor viability. 



Marked anomalies in the appearance of incompatibilities are seen in 

 the fact that one species may be highly self-fertile while another, but 

 closely related species, may be self-sterile, and hybrids between such 

 species may or may not be self-incompatible. Cases of this sort have 

 been studied by Detjen (1916). 



