238 Carter . — Studies on the Chloroplasts of Desmids. I. 
structure of the chloroplasts, and the figures of Delponte (1873) were the first 
to show any differentiation at all of the cell-contents. Delponte indicated 
the presence of ridges on the surface of the chloroplasts in Eu. ansatum and 
Eu . oblongum , but, on the whole, his figures do not give a very good idea 
of the form of the chloroplast in the genus. 
Gay (1884) gives a more distinct figure of the chloroplast in Eu. 
Didelta, var. sinuatum , but it is incorrect, since he represents in a single 
semi-cell two separate chloroplasts, each with a central pyrenoid. During 
this work the typical chloroplast of this species was found to be quite 
different. 
In practically all cases, careful staining is essential for the successful 
investigation of the chloroplasts of this genus, and with the largest species 
it is even necessary to cut sections in order to understand their complicated 
structure. After the general plan of the chloroplast has been made out by 
means of sections, it is then possible to interpret the extraordinary appear- 
ance presented by the whole specimen. 
The species examined were Eu. dubium , Nag., Eu. elegans , (Breb.) 
Kiitz., Eu. binale , (Turp.) Ehrenb., Eu. pectinatum , Breb., Eu. ansatum , 
Ralfs, Eu. bidentatum , Nag., Eu. eras sum, (Breb.) Kiitz., Eu. oblongum , 
(Grev.) Ralfs, Eu. Didelta, (Turp.) Ralfs, Eu. ampullaceum , Ralfs, Eu. 
affine , Ralfs, Eu. insigne , Hass., Eu. ventricosum , Lund., Eu. sinuosum , 
Lenorm., Eu. cuneatum , Jenner, and Eu. verrucosum , Ehrenb. It was 
found that in every case the chloroplasts are typically axile, and in all these 
species, with the single exception of Eu. verrucosum , there is only one 
chloroplast in each semi-cell. It is possible that this species, which differs 
from all the others examined, not only in its chloroplast, but also in the 
general form of its cells, should be placed in a special section of the genus 
j E nostrum. 
Excluding Eu. verrucosum, the species examined fall into two distinct 
groups according to the structure of their chloroplasts. In the first the 
chloroplast is quite simple, and contains typically a single pyrenoid in the 
central position. The larger species form the second group. Their 
chloroplasts are much more complicated, and although being nominally 
axile, have by far their greater mass disposed in a parietal layer against the 
interior of the cell-wall. The pyrenoids are numerous, and are practically 
confined to the more peripheral parts of the chromatophore. 
Although presenting very diverse appearances when examined from 
the exterior, the chloroplasts of the various species of the genus are really 
all built up on the same plan, and a comparison of transverse sections shows 
that the differences even between the two main groups are very slight. In 
fact all can be considered as elaborations of the simple type found in 
Eu. dubium, and in general the chloroplast becomes more complicated 
with the increase in size of the cell. 
