Oenothera Lamarckiana and O. gigas. 953 
, sterile when the chromosomes are of the same germ-plasm. There are 
other factors at work probably of an intricate physiological nature. 
For these reasons the writer is not impressed with the importance 
of the criticism that the partial sterility of Lamar ckiana indicates its hybrid 
origin. Partial sterility in Oenothera and related genera, as pointed 
out by Geerts, is a phenomenon so common that the significance of 
its presence or absence may readily be unduly emphasized. So far the 
hybrids of the crosses between biennis and grandiflora (Davis, Tl) which 
approach closely to Lamar ckiana have been fertile to a high degree in the 
F x generation and then have exhibited a great range in their fertility in the 
F 2 , some of them being more than 50 per cent, sterile and others apparently 
perfectly or almost perfectly fertile. The writer will lay no emphasis 
on the partial sterility of Lamar ckiana in the development of his views 
that Lamar ckiana arose as a hybrid between strains of biennis and grandi- 
flora . The behaviour of Lamar ckiana in throwing off marked variants 
in such large numbers, together with the fact that Lamarckiana is unknown 
as a clear component of the American native flora, is the chief reason for 
his belief that this interesting plant is not, as assumed by de Vries, repre¬ 
sentative of a wild species. 
Oenothera gigas. 
The first announcement that the number of chromosomes in Oenothera 
gigas is double that of the parental form Lamarckiana appeared in a note 
of Miss Anne Lutz (Science, xxvi, 190.7, p. 151), who reported the dis¬ 
covery of twenty-eight or twenty-nine chromosomes in mitotic figures of 
the root-tips. Gates (Science, xxvii, 1908,, p. 193) shortly after confirmed 
this discovery in an examination of the reduction divisions in the pollen 
mother-cells which showed the sporophytic number of chromosomes to 
be twenty-eight and the reduced number to be fourteen. The present 
study is in agreement with the above conclusions. The material with 
which these two investigators have worked, and also that described in 
this paper, is all descended from the first plant of gigas which in 1895 
appeared in the cultures of de Vries. 
Gates (’ 09 ) has published a paper chiefly devoted to a comparison 
of the cell and nuclear measurements of gigas with those of Lamarckiana , 
to test Boveri’s theory that in related forms the nuclear surface and cell 
volume in homologous tissues are proportionate to the number of chromo¬ 
somes in the types compared. In this paper is given a short account of 
that period of the reduction processes from the metaphase of the hetero¬ 
typic mitosis to the prophase of the homotypic. The unfortunate loss 
of the figures intended to illustrate this account renders impossible a close 
comparison between Gates’s description and the conclusions of the writer, 
