Snow. — Pseudo-Plenrococcus , Nov. gen. 191 
protococcoid condition, and he believes it should be classified 
as such. Zoospores, however, have not been observed to be 
formed from the filaments, and on this account it would 
seem best to separate these forms from both Pleurococcus and 
Stigeoclonium and to create a new genus. As they resemble 
Pleurococcus so closely they might appropriately be called 
P seudo-Pleurococcus. A description of two of these forms 
will here be given. 
Pseudo-Pleurococcus botryoides, Nov. sp. 
This was found on the bark of a tree near Ann Arbor, 
Michigan, in December ’ 97 , and formed a thick, dark-green, 
pulverulent covering, quite like that formed by Pleurococcus 
vulgaris. Microscopical examination showed it to consist 
of single cells and of parenchymatous masses varying in size 
from two cells up to clusters large enough to be easily 
distinguished by the naked eye (Figs. 1-6). The cells measure 
6 * 5 “ 7*8 P ln diameter. The chromatophore lines the mem- 
brane, but presents a somewhat irregular opening on one side. 
Opposite this opening lies the pyrenoid. The membrane is 
thin and gives the reaction for cellulose with iodine and 
sulphuric acid. The nucleus is single and lies near the 
centre. 
Material directly from the bark was placed under culti- 
vation in Knop’s solution of various concentrations, and on 
agar mixed with the same solution. All of these media 
possessed more moisture than was present on the bark, and the 
result was that all the cultures began immediately to produce 
filaments, one arising from almost every superficial cell (Figs. 
7, 8, 14, 15). Growth of the filaments continued for some time 
in all media alike ; but after the Alga became accustomed 
to the stimulating effects of the moisture, development varied 
according to the condition. On agar, and in Knop’s solution 
of -4% and 1%, the filaments gradually began to assume 
the parenchymatous form ; while in weaker solutions, such 
as % the filaments continued to grow and to branch, until 
o 2 
