Carter . — Shi dies on the Chloroplasts of Desmids. /. 229 
CL Siliqua , West and G. S. West, CL costatum , Corda, CL striolatum , 
Ehrenb., CL regulare , Br^b., CL angustatum , Kutz., Cl. attenuation , 
Ehrenb., Cl. Libellula , Focke, Cl. Dianae , Ehrenb., Cl. rostratum, Ehrenb., 
and Cl. juncidum , Ralfs. This has led to the conclusion that the broad 
axis figured by Lutman for CL Ehrenbergii and CL moniliferum is not 
common to all species of the genus, and furthermore that even within the 
limits of a single species the relative size of the axis and ridges cannot be 
considered as a fixed character, but is, on the other hand, liable to consider- 
able individual variation, according to the condition of the cell, this being, 
however, more pronounced in certain species than in others. 
In a few of the species examined, e.g. Cl. Lunula , Cl. lanceolatum , and 
Cl. Siliqua , the structure of the chloroplast as seen in transverse section is 
often quite similar to that figured by Lutman, but even here the axis is 
sometimes much more slender in proportion than his figures show it (Figs. 
2-5). Cl. attenuation and CL Libellula seem almost invariably to have 
chloroplasts, which in transverse section are rather more like Nageli’s 
figures than those of Lutman, in having fairly large radiating plates and 
a comparatively slender axis (Figs. 9 and 12). 
In Cl. costation , Cl. striolatum , and Cl. regulare , however, the most 
conspicuous variations in the size of the central axis occur, transverse 
sections of some individuals of these species being quite similar to those 
figured by Lutman (Figs. 30 and 34), whilst sections of other specimens 
may present the most unexpected appearance (Figs. 26-9 and 40-2). 
The axis in these peculiar chloroplasts may quite lose its definite shape as 
a more or less cone-shaped structure, the whole chloroplast in transverse 
section being irregularly branched, so that the axis appears merely as 
a strand of tissue connecting up the irregularly arranged ridges (Fig. 41). 
This strand of material, which constitutes the axis, may be very much 
swollen at intervals for the accommodation of the pyrenoids, but it is usually 
very drawn out in between. 
In all the species examined, with the exception of CL Lunula 
(Figs. 1-5), the pyrenoids occur in a single row in the middle of the central 
axis, but when photosynthesis has been going on very rapidly, and the 
pyrenoids have become very numerous, they occasionally spread in certain 
places towards the periphery ; cf. Fig. 34. In Cl. Lunula the relative 
position of the pyrenoids depends on the size of the axis of the chloroplast. 
They are usually embedded in the peripheral parts of the axis ; thus in 
cells having a broad axis and low ridges they are quite near the cell-wall, and 
in such cases are never found very far in the interior of the cell (Figs. 1 and 
2), whilst in other individuals having a very slender axis and large ridges, 
the pyrenoids are crowded together in the comparatively small axis of the 
chloroplast, which in such cases may be an almost solid mass of pyrenoids 
and starch (Figs. 3 and 4). This variation in the size of the axis and the 
