364 BOTANICAL GAZETTE [MAY 
may assume the characteristics of a typical unicellular alga, or may 
. take on the nature of a well defined branched filament. 
An alga which undoubtedly belongs in this same genus was 
found first in Basel, Switzerland, and its life history traced under 
the guidance of Professor Kies (5), but the species here given 
has been found in various places in the United States and under 
different conditions, but principally in the vicinity of Northamp- 
ton, Massachusetts. In. which phase of its polymorphism this 
alga existed in its natural habitat cannot with certainty be stated; 
its size is so minute, that its identity can be determined only in 
culture, and there the form that it assumes depends entirely on the 
cultural conditions. 
In its filamentous state it resembles most closely Conferva and 
Bumilleria in that each cell contains several chloroplasts which 
ave a peculiar light and transparent color, without starch and 
pyrenoid (figs. 1to-14). The profuse branching of this form, 
however, would prevent its being classified with either of these 
genera, which are strictly unbranched. In its unicellular condi- 
tion (fig. 15) it is doubtful if one could distinguish it from a small 
Botrydiopsis. The cells are spherical, with a number of light- 
colored, parietal chloroplasts, but the fact that it may assume a 
filamentous state would probably place it far from this form in 
the generally accepted system of classification. 
In the filamentous state so profuse are its branches that it often 
forms relatively large, more or less spherical complexes in which 
the branches radiate from a common center with apical growth. 
In a vigorously growing culture (as in 0.03 per cent Knop’s solu- 
tion) the filaments are cylindrical, and in each cell there are rela- 
tively few irregular parietal chloroplasts (figs. 11, 12). Only a 
single nucleus is present, which sometimes may be seen between 
the chloroplasts without staining. 
It has been found that the concentration of the culture me- 
dium exerts a great influence on the form the plant assumes. In 
a series of cultures made in different concentrations of Knop’s 
solution ranging from 0.05 per cent up to 1 per cent, it was found 
that from 0.05 to 0.3 per cent there was a regular increase in 
individuals, also in the length and number of filaments, which 
