202 BOTANICAL GAZETTE [MARCH 
somes in the spindle nor the definite Jengths of the chromosome 
branches are considered by Strasburger as furnishing satisfactory 
marks for contrasting typical and atypical division in metaphytes. 
Strasburger found in the pollen mother-cells of Lilium and also 
of other forms that the daughter chromosomes at the beginning 
of the metaphase undergo a second longitudinal splitting. This 
takes place at right angles to the first. 
Guignard (2) came to the same view as did Strasburger in 
regard to a second longitudinal splitting in the pollen mother- 
cells of Majas major. 
This second longitudinal splitting described as occurring in 
the atypical divisions of cells Strasburger would make a dis- 
tinguishing feature of their division, marking them out from 
typical divisions by this rather than by the form of the chromo- 
somes or by the manner of insertion. Belajeff does not assent 
to the view that there is a second longitudinal splitting, but 
holds such V’s as consisting of two chromosomes bound together. 
It is not within the province of the present investigation to 
go into the details of atypical divisions in plants. A comparison 
of Strasburger’s figures with the structures seen in the typical 
division stages of Allium confirms me in the belief that even in 
the presence of this second longitudinal splitting, we have no 
feature which will distinguish atypical from typical division. 
I think that this second longitudinal splitting, described by 
Strasburger and by other investigators as peculiar to atypical 
division, is the same phenomenon as that described by me as 
occurring in the typical division of Allium cells, namely, the 
apparent longitudinal splitting seen in the surface view at the 
beginning of the metaphase, and that it is due to the changing of 
the daughter chromosomes from tubular structures into the quadri- 
partite threads. This change is but a reversal of the change 
which occurred before the metaphase. 
Future research, I believe, will establish that the mechanism of 
cell division in both the typical and atypical forms is essentially 
the same. 
CAMBRIDGE, MAss. 
