312 BOTANICAL GAZETTE [ApRiL 
parallel projections are sent out, and these are cut off by transverse 
walls (fig. 72). 
Although the plant may be kept under cultivation as a unicellular 
alga for a period of at least three months, evidently the normal state 
is a disk form, for, though development in the unicellular condition 
was very rapid for the first few days, it soon decreased and almost 
ceased. This slow development is true also of the thalli arising from 
the zoospores when unattached ; they never attain a large size, but this 
may be due to unfavorable culture methods. 
Of different culture media tried, water, various concentrations of 
Knop’s solution, vegetable solution, and agar to which had been 
added Knop’s solution, the last medium proved most favorable, and 
development, though slow, was evident as long as the cultures were 
continued. 
Reproduction other than by means of zoospores and vegetative 
division was not observed. 
The zoospores (fig. 73) are oval or nearly spherical, though art 
times more elongated and slightly broader near their anterior extremity 
(fig. 74). They are 10.5—-15.5 ~ long and 7.8-13 p broad. Usually 
they do not exceed 10.5min breadth. They are noticeable for their 
very granular appearance, which is due to the presence of globules of 
oil; these become darkened by osmic acid, and dissolved by ye? 
form. On account of the great quantities of this oil the igre 
the chromatophore could not be determined, neither could spe 
or a pyrenoid be detected. A large brick-red eye-spot is promine? 
near the anterior end, and four cilia are present. Either four, me 
or sixteen zoospores are formed from the repeated bipartition 0 as 
contents of a cell. They are liberated by breaking through the s 
tinous membrane while still enclosed in an inner gelatinous env ah 
this, however, is quite invisible without use of reagents. They pes 
in this membrane for a relatively long period, moving almost ie 
ally. Some half dozen of these clusters were observed to ™° ined. 
three hours, but the entire period of motion was not wae oes 
During these movements they were observed to change theirs 
becoming more elongated in form, as in fig. 74. 
On coming to rest they soon become rounded, and coe 
Usually they develop directly into a disk or cluster, aS pene weft 
be, but on agar with 0.4 per cent. Knop’s solution severa som thes? 
noticed where two or four zoospores were formed directly 
begin to divide 
may 
