Somatic Mitoses in Oenothera. 
BY 
R. R. GATES, M.A., Pu.D. 
Imperial College of Science , South Kensington. 
With Plate LXXXVI. 
HE purpose of the present paper is to record certain facts regarding 
X the somatic mitoses in the Oenotheras. For several years I have 
made incidental observations on the somatic divisions, particularly in flower 
tissues. But recently, in connexion with a study of the formation of the 
megaspores in O. lately certain peculiar phenomena were observed in the 
rapidly dividing cells of the nucellus. In order to understand these peculiar 
appearances, which stood in various possible relations to the phenomena of 
reduction, it was found to be necessary to make a special study of normal 
somatic mitoses. 
A brief account of normal nuclear division in the cells of the nucellus 
will therefore be given, followed by a description of the few rare cases 
in which the shape of the chromosomes differs from the normal, and certain 
instances in which an actual reduction division is apparently taking place in 
somatic tissue. 
The slides from which these observations were made were all prepared 
from material collected in July, 1909, from a single plant of O . lata for 
a study of oogenesis. The fixing fluid used was a chrom-acetic solution 
which gave excellent fixation of the nuclei, and the stains employed were 
Heidenhain’s iron-alum-haematoxylin and the triple stain. My actual 
acquaintance with the somatic mitoses is much wider, including several 
years’ observations on a large number of forms. 
Chromosome Numbers. 
It may first be stated that the sporophyte number of chromosomes in 
this O. lata plant was 15. Several counts were made in various mother- 
cells, which yielded incontestably 15 in every case. A large number 
of counts made in the nucellar tissue showed that 15 was the characteristic 
number here also, though certain variations from that number were found to 
[Annals of Botany, Vol. XXVI. No. CIV. October, 1912.] 
