176 BOTANICAL GAZETTE [MARCH 
proposed different auxiliary suppositions. And since the possi- 
bility is acknowledged that mutability may be far more widely 
spread within this group than we now know, such suppositions 
must not be of a limited nature, but applicable to large divisions of 
the vegetable kingdom. KEARNEY, in studying the mutations of 
the Egyptian cotton, comes to the conclusion that these and other 
mutations might be the result of crosses between remote ancestors, 
but that these crosses have left no other traces in their descendants 
than ‘‘the disturbance of germinal equilibrium, which manifests 
itself in the production of mutants.’ It is not very clear how 
this supposition is to bring the problem nearer to its solution. 
In a recent article in this journal,” JEFFREY takes an opposite 
position. He assumes that the ancestral crosses have left another 
visible trace in their descendants, which is the partial sterility of 
their sexual cells. It is a well known fact that many hybrids have 
partially sterile pollen, while acknowledged species have, as a rule, 
only fertile pollen grains. JEFFREY assumes this rule to be without 
exceptions, but does not adduce any arguments in favor of this 
hypothesis. It is difficult to judge the value of an argument so 
long as the facts upon which it rests have not been submitted to 
criticism. But I might suggest that it seems rather hard to recon- 
cile this view with the fact that in angiosperms three of the four 
megaspores are usually sterile, while only one produces an embryo 
sac. Are we to deduce from this fact, in connection with JEF- 
FREY’S hypothesis, that all angiosperms are hybrids, at least on 
the maternal side ? 
Numerous special arguments could be adduced. It may suffice, 
however, to point out the genus Carex, in some of the best species 
of which the pollen is in the same condition, three of the grains of 
each tetrad being sterile and only one fertile.* Every single grain 
of the ripe pollen is a tetrad, showing the very reduced rudimentary 
remnants of three of its cells as a flattened investment of the 
fertile one. 
™ KEARNEY, T. H., Mutation in Egyptian cotton. Jour. Agric. Research 2:287- 
302. 1914. 
2 Jerrrey, E. C., Spore conditions in hybrids and the mutation hypothesis of 
DeVries. Bor. Gaz. 58:322-336. 1914. 
8 Jue, H. O., Die Entwickelung der Pollenkérner bei Carex. Jahrb. Wiss. Bot. 
35:649-056. Igoo. 
