1900] CHLOROCYSTIS COHNII 105 
is said to lie always upon but one side of the cell. This is not 
true, however, and it was only after a considerable number of 
specimens were examined that the ‘one-sided’? chromatophore 
was observed. It so happened that all the specimens which 
were first found showed a chromatophore completely lining the 
cell wall, as indicated in jigs. 7, 2, and 4g. Later, however, exam- 
ples were found more nearly resembling Reinhardt’s figures (figs. 
3, §a); but while this condition frequently occurs, it can no more 
be considered characteristic than when the whole cell is lined. 
A large and easily discernible pyrenoid lies near the surface of 
the cell and can be followed through all the subsequent divisions 
of the chromatophore (figs. 6, 7). Material killed in picric acid 
and stained for some time in 2 per cent. acid fuchsin brought. 
out the pyrenoids well, although Flemming’s fluid with. iron- 
alum-haematoxylin gave perhaps more satisfactory results. The 
chromatophore usually forms a definite dome-like thickening 
where it surrounds the pyrenoid, and this may extend into the 
cell in the way shown in fig. 5a. When the chromatophore does 
not entirely line the wall, it radiates from the pyrenoid in irregu- 
lar bands or ribbons, and these frequently do not pass more than 
half way round the cell (fig. 5a). This is the condition which 
Reinhardt figures and which he considered a generic character- 
istic. It was thought for a time that cells in which the chroma- 
tophore formed a complete lining might represent a condition 
subsequent to the formation of zoospores and not really be the 
adult Chlorocystis. Cultures in a Van Tieghem cell did not give 
much information on this subject, for although zoospores would 
be formed and escape, they did not develop to anywhere near 
Maturity. This was probably due to an insufficient supply of 
©xygen, for when cultures were made in Ward cells, or simply 
see ae cover glasses kept in a moist chamber, the zoospores 
Hse snag from the time they escaped until they attained 
in. evelopment. By this means it was settled beyond a 
ilies at in the great majority of cases the chromatophore 
rely lined the cell from the beginning, and that it was a per- 
f . 
ectly normal arrangement throughout all the vegetative stages 
of the plant, 
