300 Carter.— Sht dies on the Chloroplasts of Desmids. II. 
sharply defined, and have their free edges produced to form outgrowths of 
various shapes. The two median ridges continue for some distance beyond 
the incisions on each side of the polar lobe, but never extend quite as far 
as the nucleus. The pyrenoids are large and number from twelve to 
fifteen. 
M. apiculata , (Ehrenb.) Menegh. x 510. 
M. rotata and M. apicidata. 
The most striking feature of the chloroplasts of these two species is 
that there are two very prominent ridges on each side of the axis stretching 
right from the nucleus to the apex of the chloroplast. These are rather 
larger in M. apicidata than in M. rotata because of the relatively greater 
thickness of the cell; cf. Text-fig. with Figs. 9 and 10. In the former 
species there is in addition a series of ridges, almost equally striking, 
following the outlines of the principal incisions of the axile plate. In 
M. rotata ridges are usually wanting in the lateral lobes of the cell, and 
even if present they are only very slightly developed. The pyrenoids in 
M. apicidata usually number about thirty ; in M. rotata they are often 
much more numerous, and may be more than eighty. 
M. radiata and M. Crux- M elite nsis. 
The chloroplasts of these two species are quite similar to each other 
(Figs. 15, 17, and S3). The axile plate extends for quite a considerable 
distance into the peripheral outgrowths of the cell-wall, and has two rather 
definite median ridges projecting from both its surfaces. There are various 
other ridges (Fig. 18), very irregularly arranged, perhaps more so in the 
case of M. radiata than in M. Crux-Melitensis . In the only specimen of 
the latter species examined there were about thirteen pyrenoids in each 
semi-cell, whilst in M. radiata they vary from eight to thirty. 
