Carter. — Studies on the Chloroplasts of Desmids. III. 283 
C. achondroides differs from the first type in that the lateral lobes of its 
chloroplast are provided with pyrenoids as well as its central axis. 
In C. pseudoconnatum the chloroplast is axile with four wedge-shaped 
masses radiating towards the periphery, each mass possessing typically one 
pyrenoid. 
C . ornatum and C. Ralfsii differ from all other species examined 
having axile chloroplasts in their scattered pyrenoids. There are rarely 
more than three in the former species, but in the larger one they are much 
more numerous. The chloroplast of C. Ralfsii shows striking resem- 
blances to those found in certain thick-celled species of Micrasterias. 
Many species of Cosmarium have two axile chloroplasts in each semi- 
cell, there being one point of pyrenoid formation in each chloroplast. The 
axis which contains the pyrenoid or group of pyrenoids is surrounded by 
a number of radiating plates, or more numerous string-like projections, 
whose peripheral edges in many cases spread out over the internal surface 
of the cell-wall, either in irregular parietal masses, or as a more or less con- 
tinuous reticulated film. 
Two forms of C. praemorsum were examined, containing one and two 
chloroplasts in a semi- cell respectively. 
C. Brebissonii was found to have most peculiar and variable chloro- 
plasts, which are sometimes parietal, but in other individuals penetrate into 
all parts of the cell. 
In a few species the chloroplasts were found to be entirely parietal, with 
scattered pyrenoids. In such species the number of chloroplasts and 
pyrenoids present is variable. 
In conclusion, I wish to express my gratitude to the Birmingham 
Natural History Society, and also to the Royal Society, for grants to help in 
the cost of reproducing the plates illustrating this work. I have also to 
acknowledge the invaluable help which I received during this investigation 
from the late Professor G. S. West, who not only identified all the species 
examined, but also provided some of the material. 
Bibliography. 
de Bary, A. (1858) : Untersuchungen iiber die Familie der Conjugaten. Leipzig, 1858. 
Delponte, J. B. (1873) : Specimen Desmidiacearum subalpinum. Augustae Taurinorum, 1873. 
Memor. d. R. Accad. d. Scienze di Torino, ser. 2, xxviii. 
Ducellier, F. (1917) : Notes sur le pyrenoide dans le genre Cosmarium Corda. Bulletin de la 
Soci^te Botanique de Geneve, 2 me serie, vol. ix, 1917. 
Gay, F. (1884) : Essai d’une Monographic locale des Conjuguees. Montpellier, 1884. 
Klebs, G. (1879) : Uber die Formen einiger Gattungen der Desmidiaceen Ostpreussens. Schriften 
d. Physik. Oek. Gesellsch. zu Konigsberg, 1879. 
