158 BOTANICAL GAZETTE [FEBRUARY 
WEBBER’s second explanation was disproved by Emerson’ as follows. A 
colorless, sugary type, CCrrsusu, was used as female parent in a cross with a 
colorless, starchy type, ccRRSuSu. The resulting grains were red, starchy, 
save for a few aberrant grains which were red in part and colorless in part 
but starchy throughout. WEBBER’s second explanation fails here, since fusion 
of the second male nucleus with only one of the polars would produce grains 
which were red, starchy in part (from male nucleus fused with one polar) 
and colorless sweet in part (from independent polar). 
These two critical experiments serve to disprove WEBBER’S explanations 
and demonstrate that the normal program of double fertilization is invariable 
in corn, The next thing which was invoked to explain these aberrant grains 
was ‘‘somatic mutation” in the endosperm, but for several reasons this was 
unsatisfactory as an explanation. 
Emerson’ has finally obtained critical evidence which indicates a very 
satisfactory explanation of the phenomenon. The factor wx for waxy endo- 
sperm (Wx, corneous endosperm) is known to be carried on the same chromo- 
some with the C factor. A cross was made between a colorless, waxy female 
Parent, c-wx c-wx and a red corneous male parent, C-Wx C-Wx (the R 
e 
was of the formula c-wx C-wx C-Wx. If non-disjunction (passing of both halves 
of a divided chromosome to one pole) occurred in connection with the third of 
these chromosomes, one of the resulting nuclei would be diploid for this chromo- 
some set. c-wx c-wx, and the other tetraploid, c-wx c-wx C-Wx C-Wx. Endo- 
sperm produced by the former should be colorless, waxy; endosperm produced 
by the latter should be red, corneous. Emerson obtained aberrant grains which 
the previous ones, indicates that Sccational non-disjunction is the explanation 
of these aberrant grains. The frequency of these particular aberrant grains 
is one in 423, and one may expect non-disjunction to take place in connection 
with some one chromosome in the corn endosperm in about one of every four- 
teen grains. Direct cytological demonstration is to be hoped for. Non- 
times i i 
a 
kingdoms. Possibly the triploid nature of endosperm furnishes an especially 
favorable condition for its occurrence.—M. C. COULTER. 
Prairie vegetation.—The prairies of Illinois, occurring as they do on the 
tension line between great forest and and grassland formations of North 
America, afford peculiar advantages in the study of the development of this 
3 Emerson, R. A., Anomalous endosperm development and the phenomenon 
of bud sports. Zeit. Induk. Abstamm. Vererb. 14:241-259. 1915. 
™ EMERSON, R. A., Genetic evidence of ae chromosome behavior in maize 
endosperm. Acaee ee Bot. 8:411-424. fig. I 21 
