460 Smith. — Cytological Studies in the Protococcales. /. 
into two parts, each of which rounds up like the original pyrenoid. This 
pyrenoid division is followed by a division of the chromatophore into two 
parts. Repeated transverse divisions in the protoplasm produce a single 
row of 32 cells within the old mother-cell wall. This is followed by the 
longitudinal division of 30 of these cells, the two terminal cells again 
dividing transversely, thus forming 64 cells in all. Longitudinal division 
may occur, however, after 4, 8, or 16 cells have been formed by transverse 
division, but there is always a longitudinal cleavage of the cells at the end 
of the series of transverse cleavages. Lambert finds in C. cylindricum , Lamb , 
that there are two chromatophores containing oil drops, but no pyrenoids, 
and that the nucleus is located between the chromatophores. By repeated 
transverse divisions the contents of the cell form 8, 16, or 32 parts, and then 
there is a series of longitudinal divisions. Another type of spore-formation 
in which the contents of the mother-cell form j 00-2,000 small zoospores is 
also found in this species. 
Material and Methods. 
The material for this investigation was collected from a small sluggish 
stream on the campus of the University of Wisconsin, where the alga was 
found growing abundantly on blades of grass lying in the water. The shape 
and dimensions of the cells agree very well with Characium Sieboldii , 
A. Br. (1). The blades of grass were cut into pieces about a half-centi- 
metre long and then dropped directly into the fixing fluid. Several different 
fluids were tried, but Eisen’s weak solution, prepared according to the 
formula of Timberlake (8), proved the best. After embedding in paraffin, the 
material was cut on a microtome into sections from 9 to 12 microns thick. 
II eidenhain’s iron-alum -haematoxylin gave fairlygood results, but Flemming’s 
safranin-gentian violet-orange G combination proved much better. The 
best preparations, however, were obtained by substituting light green FS 
for the orange G in the Flemming’s triple stain. 
The Structure of the Cell. 
The chlorophyll in the species studied is not located in a definite 
chromatophore, but apparently evenly distributed throughout the cell. The 
cytoplasm is not visibly alveolate in structure at any stage of development, 
but has always a uniform granular structure. 
There is no uniformity in either the shape or location of the pyrenoid. 
In certain cells the pyrenoid is spherical (PI. XI, Figs. 3 and 6), in others 
variously lobed (Figs. 1, 2, and 9). Although the pyrenoid of the algae is 
generally reported as being spherical, Timberlake (10) has found that in cells 
of Hydrodictyon that are forming starch rapidly the pyrenoids are apt to be 
angular, while I have found the same thing in Scenedesmus obliquus (Turp ), 
Ktz.,and S. quadricauda (Turp.),de Breb. ( 7 ). The pyrenoid of Characium 
