Carter. — Studies on the Chloroplasts of Desmids. I. 241 
Most of the largest species examined have chloroplasts of this type, 
including Eu. eras sum , Eu . oblongitm , Eu. Didelta , Eu . ampidlaceum , 
Eu. affine, Eu. insigne , Eu. ventricosum , Eu. sinuosum , and Eu. cuneatmn. 
There is remarkable uniformity in the structure of the chloroplasts in 
typical specimens of all the above species, that of the last-mentioned being 
the only one which differs even slightly from the general type. 
Although the form of the chloroplast is so very constant throughout 
the whole group, in each individual species there is considerable variation, 
the same kind of variation being met with in every case. Specimens whose 
chloroplasts are transitional between the axile and parietal conditions are 
frequently found in most of the species mentioned above. 
Putting aside such exceptions, and taking the ordinary axile form 
of chloroplast found in Eu. crassum as a type, it is seen that the massive 
chloroplast has a central axis running through the interior of the semi-cell 
from nucleus to apex ; cf. Fig. 100 (lower semi-cell). This gives off four 
radiating plates, two going towards each front face of the semi-cell (Fig. 101). 
On reaching the cell-wall each of these radiating plates spreads itself 
out against the surface of the wall, forming an extensive parietal plate, two 
of which can be seen in the front view of the semi-cell ; cf. Fig. 100 (upper 
semi-cell). This parietal portion, consisting of four plates, forms by far the 
more massive part of the chloroplast, the central axis and radiating plates 
being very thin and difficult to distinguish in whole specimens. 
The central axis usually has the form of a long narrow flattened plate 
or slender rod which is in close connexion with the nucleus near the 
isthmus, and often extends nearly to the median incision of the apical 
lobe. When more or less plate-like, it varies in its disposition, sometimes 
presenting its surface to the observer in the front view and sometimes 
its edge. Very often it is twisted at some particular point through an 
angle of 90°, so that for part of the way one sees its surface, and for the rest 
of the way its edge; cf. Figs. 63, 72, and 100. It is very common for two 
such twists to occur, one a little way from the nucleus and the other 
a similar distance from the apex. 
Occasionally, especially in Eu. Didelta , the central axis is much 
broader than usual, and forms an extensive plate in the middle of the cell. 
In transverse sections such an axis is seen as a thin line parallel to the front 
walls of the cell, giving off at each end two extremely short radiating plates 
which spread out almost immediately to form the parietal part of the 
chloroplast (Fig. 65). Thus there is a concentration of chloroplast substance 
towards the sides of the cell, and this fact is also apparent from an examina- 
tion of the whole specimen in the front view, because two dark lines are to 
be seen stretching from the nucleus to the apex, one on each side of the 
median line. In such cases it is very difficult to demonstrate the presence 
of the central axis of the chloroplast. It cannot as a rule be seen at all in 
