1918] CURRENT LITERATURE 285 
Another similarity with the Oenothera situation is that in this Drosophila 
race there would occasionally appear recessive mutants on one of these two 
“lethal chromosomes.” These recessive mutants, however, could not become 
manifest on account of the enforced heterozygosity. They could only become 
manifest when crossing over occurred and homozygosity was thus made pos- 
sible. ‘As crossing over occurs with predictable frequencies, those individuals 
showing characters abnormal to the stock were thrown continually in a definite, 
very small percentage of cases.” In just such a regular, although small, per- 
centage of cases does Oenothera Lamarckiana throw its mutants. LLER con- 
cludes that the Oenothera situation is to be explained by a similar mechanism, 
“but Pmemy the lethal effect in Oenothera is on the gametes rather than on 
the zygote 
A sioiitas idea appears in a paper by Davis,‘ in which we find summarized 
some of the evidence, old en sak on the suspected hybrid nye of 
Oenothera Lamarckiana. The regularity with which the same old mutants 
are thrown and the production a twin hybrids in crosses suggest to this aise 
the hybrid condition of O. Lamarckiana. The facts that about one-half of 
both pollen and ovules, in random distribution, are oie and that only 30-40 
per cent of the seeds produced are fertile, suggest that only such gametes and 
zygotes are fertile as will reproduce the hybrid type. The argument is essen- 
tially similar to that of MuLLER. “If it could be shown that in every group 
of 4 pollen grains (tetrad) formed as the result of the reduction mitoses only 
2 grains are perfect, the conclusion would be justified that pollen sterility was 
the result of this segregation division.’”” The author regards this as impossible, 
however, since abortion takes place after the tetrads have lost their identity. 
On this point we may quote from a review which appeared in this journal’ 
on some work of GrErts. ‘In Oenothera Lamarckiana 50 per cent of the 
ovules are found to degenerate and about 50 per cent of the pollen grains, ‘wo 
from each tetrad of spores.’ 
It begins to look more and more probable that our classic illustration of 
q 
are finally interpreted by the Mendelian system, and there is now much hope 
that this may soon come to pass.—MERLE C. COULTER 
Edible and poisonous mushrooms.—Popular interest in the fleshy fungi 
appears to be growing in many sections of the country. This interest may be 
attributed to several different causes, chief of which are to be found in the 
* Davis, B. M., A criticism of the evidence for the mutation theory of De VRIES 
from the behavior of species of Oenothera in crosses and in selfed lines. Proc. Nat. 
Acad. Sci. 3:704-710. 1917. 
7 Bor. Gaz. 47:481. 1909. 
