VOLUME LI NUMBER 6 
THE: 
BOTANICAL ‘GAZETIE 
JUNE r911 
CELL AND NUCLEAR DIVISION IN CLOSTERIUM 
B. F. LUTMAN 
(WITH PLATES XXII AND XXIII AND ONE FIGURE) 
Historical 
The first figures showing division in desmids were those of 
Cosmarium by EHRENBERG (11). Those. drawings, while not 
entirely accurate, indicate clearly that he saw the two new daughter 
half-cells being interpolated between the old ones. Each half of 
the parent cell was evidently considered by him as an individual, 
since his genus description states that the individuals are arranged 
in the colonies “‘in chains of two or four.” | 
NAcEtt (33), RALFS (35), and Fock (17) observed cell division 
in the desmids and gave fairly complete accounts of the process. 
DeBary (9) did not describe division in detail, but mentions the 
fact that the newly formed transverse wall of Closterium and Penium 
is flat, and that the new end grows out as a cone-shaped structure. 
As the chromatophore is divided into two parts, some of the older 
observers, as EHRENBERG, regarded the mature plant as a chain 
of two cells, but DEBARY was clear on this point and recognized 
the desmid as a single cell with a nucleus between the halves. 
Nothing was observed by any of these investigators as to the 
conduct of the nucleus during division, as the importance of that 
organ of the cell was not yet fully recognized. 
It is to ALFRED FISCHER (14) that we owe our first knowledge 
of the details of the process as it occurs in this genus. FISCHER 
found the cross-wall formed in essentially the same manner that 
STRASBURGER had described for Spirogyra. It appears soon after 
4or 
