88  Self-Incompatibility 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°/,, 1:1°/,, 1:6°/, and 0:0°/,. In the next 
generation three offspring of the plant 43:1 °/, self-fertile were all self- 
fertile (15:5°/,, 20°0°/, and 11:8 °/,), and the three offspring of the plant 
1:1°/, self-fertile were 0°7°/,, 0°5°/, 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-fertility, which is merely another way 
of saying that they are fluctuatingly variable in their self-com patibility. 
- Heribert-Nilsson finds evidences of degeneration in self-fertilized 
lines, both in the quality and viability of seed, 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 Z, which were most vigorous iD 
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°/,, 28°6°/,, 14°6°/,). It is, however, stated that all 
seeds of the I, 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). 
