194 Snow. — Pseudo-Pleurococcus , Nov. gen. 
a filamentous cluster transferred to agar changed completely 
to the unicellular condition. 
This form resembles Pleurococcus vulgaris greatly. It also 
resembles the illustrations of the form described by Chodat ; 
but as this contains a pyrenoid, and none was found in the 
species he studied, it cannot be the same. 
If these filamentous forms be regarded as a genus separate 
from Pleurococcus , the genus would be characterized as 
follows : — 
Pseudo-Pleurococcus, Nov. gen. 
Thallus, in the atmosphere either unicellular or forming 
parenchymatous masses of cells of various size ; in liquid 
media filamentous. Cells 6-5-8 [jl in diameter. Chromatophore 
parietal, but not completely lining the membrane. Nucleus 
single. 
P seudo-Pleurococcus botryoides , Nov. sp. 
In atmosphere occurring as single cells, or forming dense 
clusters of various size ; in liquid media profusely branched, 
the branches arising laterally from the filaments. Cells 
6-5— 7-8 /x in diameter. Chromatophore in the single cells 
reduced, pyrenoid present. On bark of trees near Ann 
Arbor, Michigan. 
P seudo-Pleurococcus vulgaris, Nov. sp. 
In atmosphere occurring as single cells, or in cell-complexes 
of four or multiples of four ; in liquid media branched, but 
not profusely so, the branches originating by the division of 
the apex of a terminal cell. Chromatophores line but a por- 
tion of the membrane in each cell of the filament ; often two 
or more occur in a single cell. Diameter of cells 6-5 j u ; 
pyrenoid present in the chromatophore. On bark of trees in 
Basel, Switzerland. 
