284 BOTANICAL GAZETTE [SEPTEMBER 
the hexoses show increase. The curves for hexose, starch, and this dextro- 
rotatory material are intimately related and indicate interconvertibility; the 
last-named substance may be a protein or a gum standing in causal relation to 
starch synthesis. 
In the leaves the daily fluctuations of alcohol-soluble substances is through 
a range almost twice as great as that of total sugars. In the stalks the same is 
true, in which respect the potato is unlike the mangold. The dextrose-levulose 
ratio determinations are of little significance because of the presence of laevo- 
rotatory non-sugars, probably asparagine, but the authors regard them as being 
a 
presence of impurities of the same character. Levulose apparently pre- 
dominates in the leaves and dextrose in the stalks, by reason of the accumula- 
tion of dextro-rotatory stuffs in the latter, or possibly by reason of an actual 
excess due to the using up of levulose in tissue building. That this latter 
alternative is the correct one is indicated by the fact that the determinations 
of cane sugar by polarization and by reduction are in close agreement.— 
JoserH S. CALDWELL 
The Oenothera situation—Three recent papers have cast some light on 
the perplexing Oenothera situation. One of the most serious objections to the 
mutation theory has been that mutants which have appeared under observa- 
tion in artificial cultures have regularly been interfertile, while incipient ash 
in nature are essentially intersterile. Mertz and BripcEs‘ have shown that 
mutants may be intersterile, describing two cases in Drosophila, Hig cain 
two mutants fia either refuse to cross or else give sterile hybri 
MULLER’ has explained a curious case in Drosophila, w which strikingly 
resembles the Oenothera situation. A certain race of Drosophila breeds prac- 
tically true, and yet it isin a heterozygous condition. This paradox is explained 
by “balanced lethal factors,” a given chromosome and its allelomorph each 
carrying lethal factors. When one of these factors is present in a zygote it 
brings death, but when both factors are present they are antagonistic in their 
action and the zygote develops into a mature individual. Thus the homo- 
zygotes, which are thrown off every generation, die in infancy, since they con- 
tain single lethal factors; only the heterozygotes survive, for in them alone 
are the lethal factors balanced and inactive. The result is that the hetero- 
zygous race seems to breed true. This balanced race, as we should expect, 
gives in crosses twin hybrids as in Oenothera crosses, while crossing two such 
balanced races in Drosophila gives multiple hybrids, as also occurs in Oenothera. 
4 Metz, C. W., and Briwces, C. = , Incompatibility of mutant races in Drosophila. 
Proc. Nat. Acad. Sci. 3:673-678. 1 
5 MuLteR, HegMann J., An Pa eS case in Drosophila. Proc. Nat. Acad. 
Sci. 3:619-626. 1917. 
