Carter .■ — Studies on the Chloroplasts of Desmids. /. 233 
type gives a certain amount of rigidity to the chromatophore, and when 
the starch disappears the reticulum of the chloroplast collapses and the 
ridges become thinner but more plate-like as the axis decreases in size. In 
this condition they are unable to preserve their original straight paths from 
end to end of the chloroplast, but from lack of internal support bend 
irregularly all down the cell. 
The distending of the chloroplast with starch-grains may occur in any 
species of Closterium , or indeed in any other Desmid, and although, so far, 
it has only been observed to influence the form of the chloroplast to any 
great extent in Cl. costatmn , Cl. striolatum , Cl. regulare ) and Cl. angustatum , 
it is quite probable that the examination of other species of the genus at 
various seasons of the year will show that the phenomenon is quite general 
with this type of chloroplast. 
Slight undulation of the ridges is also sometimes observed in some of 
the smaller species in which the ridges are scarcely large enough to allow of 
real anastomosis. Thus in some individuals of Cl. Dianae and CL rostratum 
the ridges undulate in this way, whilst in others they do not. Probably this 
difference is also due to the same variation in the starch-content of the 
chromatophore. 
Although the variation in the size of the axis is usually to be correlated 
with the amount of stroma-starch contained in it, yet in the two large 
species Cl. Lunula and Cl. Ehrenbergii this is not so. For in these species 
there is also great variation in the size of the axis of the chloroplast, the 
protoplasmic network of the chloroplasts of individuals having broad 
radiating plates and a comparatively slender axis being usually in the form 
of a very fine, compact reticulum, but where the axis is much broader the 
protoplasmic network is very coarse; cf. Figs. 2 and 4. In the latter case 
the appearance is not due to the presence of stroma-starch, but simply to 
the extreme vacuolation of the protoplasm. 
In material containing a quantity of Cl. Ehre 7 ibergii and a little 
CL moniliferum , which had been stained in the usual way, it was noticed 
that practically every individual of the former species contained countless 
numbers of small darkly staining granules, similar to those previously 
observed in species of Cpsmarium. They are usually found in large 
numbers in the narrow ridges of the chloroplast quite near the cell-wall 
(Fig. 44), and never occur very far in the interior of the cell. In some 
individuals they are not so numerous as in others, and possibly vary in 
number and size according to the state of nutrition of the cell. In Cl. 
moniliferum there are sometimes similar rather smaller globules in exactly 
the same position in the peripheral region of the ridges. Occasionally 
such darkly staining globules have been observed in CL Lunida , but they 
were not so common in this species as in CL Ehrenbergii . 
