Igo] EREMOSPHAERA AND EXCENTROSPHAERA 321 
Ulothrix spores is striking, but the much larger size, the arrange- 
ment of the chromatophores, and suosequent development make 
it an easy matter to differentiate this plant from that genus. 
The numerous large chromatophores are crowded near the 
surface of the cell, and are usually arranged radially (figs. 27, 
23, 24). As the cells assume irregular shapes the chromato- 
phores may be distributed in various ways, and there are often 
lacunae between the chlorophyll masses. Sometimes there are 
several layers of chromatophores, so that except for the nucleus 
and a small amount of protoplasm, the cell is almost filled with 
these bodies. There are numerous minute pyrenoids in each 
chromatophore, but these are not readily made out without the 
use of stains. The densely packed chromatophores render it 
difficult to see the centrally placed nucleus, with its nucleolus, 
but sections (fig. 25) or crushing will usually reveal it. When 
the cells are about to form spores the nucleus divides repeatedly 
(fig. 26), then the chromatophores break up, and ina short time 
the-entire cell has a homogeneous appearance similar to that 
shown in fig. 27. The spores, which are formed from this con- 
dition simultaneously, are 2-3 in diameter, non-motile, and 
without a red spot. They escape through a hole formed by 
the dissolution of the wall (fig. 22), and in about a month 
increase to the size of the mature plants. The developing spore 
usually remains spherical until it has reached its maximum size, 
and not until then does it begin to take on the irregular shape 
previously referred to. 
The wartlike projections on the wall, reported by Chodat 
(1), frequently occur in plants after maturity has been reached, 
but in small spherical forms are quite rare. These formations 
are made up of a series of layers of cellulose, and often increase 
until they are of considerable size (figs. 23, 24). ; 
Resting conditions, with a very thick wall and of a reddish 
color, were found in pure cultures, but the mode of development 
has not been observed up to the present time. As previously 
stated, this plant has been cultivated in a pure state for several 
years, and all the methods resorted to in an effort to bring about 
