Pollen Formation in Oenothera gigas. 
BY 
REGINALD RUGGLES GATES, M.A., Ph.D. 
With Plates LXVII-LXX. 
Introduction. 
I N a paper published two years ago (’09 a ), the writer ’showed that the 
appearance of the tetraploid number of chromosomes in Oenothera 
gigas is accompanied by an increase in the size of the nuclei and cells 
of this mutant as compared with O. Lamar ckiana, the parent form. This 
increase in size was found to vary for different tissues. The respective 
average volumes of the cells were approximately 2 : i in the case of the 
epidermal cells of the petals. This was in harmony with Boveri’s law 
deduced from experimental cytological studies upon sea-urchin eggs, in 
which a doubling in the number of chromosomes was accompanied by 
a doubling in the volume of the cells, and in the surface (not the volume) 
of the nuclei. This numerical relationship was not found to hold, however, 
in Oenothera gigas in most of the tissues measured. Rather it was found 
that, in the pollen mother-cells, the volume of the nuclei was doubled, 
while the respective volumes of the mother-cells themselves were 1-5:1. 
In other tissues the ratios of the average cell volumes in O. gigas and 
O. Lamarckiana were in one case 3:1, in another tissue 3-67 :1, and in 
still another 3-83 : 1. The volumes of the nuclei in the last cases have not 
yet been measured. Without outlining further the results of the paper 
mentioned, it may be stated that I concluded that the gigantic stature of 
O. gigas resulted from the larger size of its cells and nuclei, which in turn 
was in direct relation with the presence of the tetraploid number of 
chromosomes. 
In complete harmony with the law for the nuclei in the pollen mother- 
cells of O. gigas and O. Lamar ckiana, namely, that the doubling in the 
number of chromosomes is accompanied by a doubling in the volume of 
the nuclei, Tischler (TO) has recently found that in races of the Banana 
having respectively 8, 16, and 24 chromosomes, the volumes of the nuclei 
are as 1 : 2:3. The work of the Marchals (’ 09 ) has shown in the same 
manner in Mosses, that with the appearance of the tetraploid or octoploid 
[Annals of Botany, Vol. XXV. No. C. October, 1911.] 
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