1918] CURRENT LITERATURE 461 
Self-sterility——East and Park} have recently published the results of 
some extensive experiments on 4 self-sterile species of Nicotiana, and have pro- 
posed an explanation. In the past there have been several attempts to inter- 
pret self-sterility as a response to environmental factors, notably humidity. 
Such interpretations may have been quite true in some cases of self-sterility, 
where only a single race of plants has been involved, but highly unsatisfactory 
in explaining cases where pollen fails on own stigmas and functions on stigmas 
of another race. It is such a situation that the authors have dealt with, and 
they have shown conclusively for their material that self-sterility is inherited. 
Normal seasonal changes at times induced “pseudo self-fertility ” in their self- 
sterile races, but ‘other a fatiors appeared to have little or no 
influence on self-fertilit 
As to the shyeloicated nature of self-sterility, the authors state that it is 
involved with rate of pollen tube growth. This in itself suggests that self- 
sterility behaves as a sporophytic character. The fact is more definitely 
demonstrated, however, “by the behavior of reciprocal matings, pairs of 
_ Teciprocals always giving like results either when fertile or sterile.” 
Going further, the authors state “that modern discoveries tend more and 
more to show that the sole function of the gametophyte of the angiosperms is 
to produce sporophytes. The characters which they possess appear to be 
wholly sporppny ts, ithe aceenae which they carry functioning only after fer- 
tilization.” Thi ms directed at such theories as that of BELLING, 
who has given us a striking scislaiaiion of “semi-sterility” in beans, on the 
basis of the direct influence of the germinal equipment of gametophytes upon 
the gametophytes themselves. It is quite probable, however, that the two 
cases are involved with distinctly different phenomena, since BELLING’s 
material showed degeneration and sometimes complete abortion in pollen and 
embryo sacs, while the Nicotianas of East and Park were self-sterile merely 
because of the failure of pollen tubes. The hereditary mechanism of the two 
cases must be quite different. 
To explain the hereditary behavior of their Nicotianas, the authors have 
assumed a mechanism involving multiple allelomorphs and crossing over. If 
two plants differ in but one of a number of effective factors, they are fertile 
in intercrosses. “Intrasterile classes” are composed of individuals which 
differ in none of the effective factors. Anything like a thorough appreciation 
of this theory can be obtained only from the original article. 
This explanation seems sufficiently accurate in interpreting the results of 
the authors, as well as the results of some of the earlier investigators. From 
a practical point of view, however, it seems rather unsatisfactory, since it con- 
siders only the behavior of self-sterile plants when bred inter se. The authors 
3 East, E. M., and Park, J. B., Studies on self-sterility. I. The bebavior of self- 
sterile plants. Genetics 2:525-609. 1917 
