316 BOTANICAL GAZETTE [APRIL 
sort, and these with poor pegs, are formed in darkness. Even if a thallus raised 
in darkness be afterward lighted, it forms no divergent rhizoids; and if such a 
thallus after being cut off regenerates itself, the new part forms none; the power 
once lost seems finally gone. Rhizoids cut off are not regenerated, but new ones 
are formed, either from surface cells of the thallus or from a cell internal to the 
pegs occur even in true divergent rhizoids, which indicates to the reviewer that the 
possession of rhizoids of two kinds has been overvalued as a marchantiaceous 
sega for example in the case of Monoclea. 
e the formation of rhizoids on the under side of gemmae is promoted by 
aie the hairs themselves are not geotropic, but are highly sensitive to light, 
being negatively phototropic even in weak red light, but strangely enough, not 
in blue light. The divergent rhizoids of the thallus are very mies phototropic 
(negative). ‘The appressed rhizoids show no tropisms.—C. R 
The origin of Oenothera gigas.—GArTEs”? has investigated the relation of the 
number of chromosomes in Oenothera gigas to its size. This mutant from 
O. Lamarckiana has double the number of chromosomes (28) possessed by the 
parent form and by the other mutants examined. In every tissue examined, the 
cells of the mutant are conspicuously larger than those of the parent form, and the 
nuclei of the pollen mother cells during synapsis are about twice as large. The 
author suggests that increase in the size of nuclei and cells, preted upon or 
coincident with the doubling of the chromosome number, and c in the rela- 
tive dimensions of the cells in some cases, will account for all ‘Se differences 
between the two species. There is no evidence of the r resence of ncw or additional 
unit characters in O. gigas. It is concluded that the facts strongly support the 
view of the independence and genetic continuity of the chromosomes, whatever 
may be their rdle in heredity. It is suggested as most probable that the double 
number of chromosomes in O. gigas originated soon after fertilization, by the fail- 
ure of a nucleus to complete its division after the chromosomes had divided. This 
doubling of the number of chromosomes, the author thinks, ‘‘cannot be a common 
method of species formation, and bear no necessary relation to the general pro- 
cesses of evolution in the anes ” He speaks of it rather as an incident mong 
evolutionary phenomena.—J. M. C. 
Farm water supplies.—The Bureau of Plant Industry has been cooperating 
with the Minnesota State Board of Health in an investigation of the farm water 
supplies of that state, and a report by KetteRMAN and WHITTAKER has now been 
published.*3 Numerous cases and their details are presented, classified under 
22 GATES, REGINALD RuccLEs, The stature and chromosomes of Oecnothera gigas 
DeVries. hehe, fiir Zellforschung 3:525-552. ~ 
23 KELLERMAN, Kart F., AND WHITTAKER, H. A., Farm water supplies of — 
sota. Bull. 154, Bur. Pl. iad, U. S. Depart. sd pp. 89. figs. 73. 1999- 
