Igr0] LUTMAN—CELL STRUCTURE OF CLOSTERIUM 243 
quently assumed that they may arise de novo in the chromatophore, 
or at least arise from bodies too minute to be seen with the micro- _ 
scope. The apparent disappearance of the pyrenoids is character- 
istic of the time of spore formation and has been observed by Srras- 
BURGER (20) in Cladophora, Kiess (11) in Chlamydomonas and 
in Hydrodictyon, and Overton (18) in Volvox. They reappear y 
when the spores begin to grow again and apparently arise de novo. 
The commonly accepted view as to the formation of starch around 
the pyrenoid, as given by OLTMANNS, is that of Scumirz. “The 
origin of the starch layer out of the individual grains is very difficult 
to follow. If algae are taken from which the starch has been removed 
and put under favorable conditions for observation, there will at first 
appear, according to Scumirz, little round grains that are isolated 
from one another but which later grow and flatten themselves through 
Pressure on each other.’’ In contradistinction to this view is that of 
TIMBERLAKE (21), who found segments of the pyrenoid of Hydro- 
dictyon breaking off and becoming converted into starch grains by the 
deposition of starch in each segment so cut off. . 
TIMBERLAKE has described many of the pyrenoids of Hydrodictyon, 
especially where starch formation was going on rapidly, as having 
two or three concentric layers of starch around them. In Clado- 
phora (22) he has described the pyrenoid as a double convex lens- 
shaped body, from which starch grains are cut off first on one side 
and then on the other. These grains not being removed at once 
may form several layers of starch on éither side. All the other 
Pyrenoids so far described, such as those of Spirogyra, Zygnema, etc., 
have only a single layer of starch around them. 
B&tscuxi (2) has recently made a careful study of the setenv ion 
bodies of Euglena, and has founds that in preserved material they 
break up into a number of disks which he regards as due to their 
internal structure. 
The staining reactions of the pyrenoids are quite interesting and 
have been described by TIMBERLAKE (21). The pyrenoid stains a 
brilliant red in the triple stain, while the starch around it, and in the 
stroma, is colored as bright a blue. 
Némec (16) has called attention recently again to the reaction 
of starch to gentian violet, but uses a more complicated technique 
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