216 Carter. — Studies on the Chloroplasts of Desmids. I. 
two new sub-genera, Pleurotaeniopsis and Pleurenterium , to include those 
species of Cosmarium and Staurastrum respectively which have parietal 
chloroplasts. Cosmarium and Staurastrum , in the restricted sense of 
Lundell, contained only those species with axile clPoroplasts. 
The figures given by Delponte (1873) for such genera as Desmidium 
and other filamentous Desmids give one quite a good idea of the structure 
of the chloroplasts, whilst in many species of Closterium , Penium , Netrium , 
Staurastrum , and several species of Cosmarium , the form of the chloroplast 
is also indicated. 
Klebs (1879) illustrated the ridged nature of the chloroplasts and the 
position of the pyrenoids in many species of Clostermm and Penium , and 
also gave a figure of Cosmarium de Baryi , Arch., which is quite comparable 
with that given some years later by Liitkemuller (1893). 
Schmitz (1882), in his work Die Chromatophoren der Algeria only 
just mentions Desmids as having chloroplasts of very diverse forms, which 
usually consist of a central axile portion provided with radiating plates of 
various kinds. 
Gay (1884) figured the chloroplasts in a few species of Closterium , 
Penium , and Micrasterias , and also in species of several other genera. 
An attempt to subdivide the genus Xanthidium , similar to that of 
Lundell (1871) in connexion with Cosmarium and Staurastrum , was made 
by Boldt (1888), who included in a new sub-genus ,Euxanthidium, all species 
of the genus having parietal chloroplasts, and in Centrenterium all species in 
which the chloroplasts are axile. Boldt described a new species of Xanthi- 
dium, X. groenlandicum, Boldt, which he placed in the sub-genus Centren- 
terium, evidently believing it to have axile chloroplasts. The same species 
has been figured again by Larsen (1907), and although these figures are not 
particularly good for the chloroplasts, they do indicate, together with his 
description, that the chromatophores in this species are really very similar 
to those of other species of the genus which have parietal chloroplasts. 
Lagerheim (1888) raised the sub-genera Pleurotaeniopsis and Pleuren- 
terium of Lundell to the rank of genera. 
Liitkemuller, who did some careful work on Desmids, published in 
1893 a detailed account of the chloroplasts in certain species of Cosmarium , 
and also in a few other species formerly placed in Lagerheim’s genus 
Pleurotaeniopsis . This was followed in 1895 and 1903 by a complete review 
of the genus Spirotaenia, and in this work the obscure structure of the 
chloroplast in those species belonging to the Polytaeniae was for the first 
time elucidated, and it was definitely shown that in these species of Spiro- 
taenia the chloroplasts are really axile, in spite of the fact that the genus 
was originally supposed to be characterized by the fact that its chloroplasts 
are in the form of spirally twisted parietal bands. 
These investigations of Dr. Liitkemuller may be regarded as the only 
