400 MR. G. 8. WEST ON 
find dealing entirely with this subject, and in it he confines his 
attention to the number of pyrenoids in the genus Cosmarium, 
the chromatophores of Penium minutum, Cleve*, and of Pleuro- 
teniopsis. In reference to the latter he advocates further 
enquiry into the structure of the chromatophores of those genera 
of Desmids which include species possessing parietal chlorophyll- 
plates. In a paper entitled “ Observations on the Conjugate ” f 
mention will be found of the occurrence of irregularities in the 
chromatophores of two species of Cosmarium—C. ornatum. and 
C. sphagnicolum. 
In the description of a species of Closterium it is customary 
to note the average number of pyrenoids in a semicell, and the 
character of the moving granules in the apical locellus or 
vacuole. No doubt these features are of some value as minor 
specific differences, and perbaps in many cases are quite as re- 
liable as the more marked peculiarities of the species of other 
genera; yet I would point out that they are subject to con- 
siderable variation, and are, therefore, deserving of more careful 
study than that usually afforded them. 
The following observations on Closterium Venus, Kuetz., were 
made on specimens from Baildon, W. Yorks. Out of 500 in- 
dividuals examined 71 per cent. possessed two pyrenoids in each 
semicell, that is to say, two pyrenoids in each chromatophore. 
The next in frequency, although much scarcer (only 16 per cent.), 
were those possessing one pyrenoid in each chromatophore. 
This is illustrated by the following table :— 
Number of Pyrenoids. Number of Sp timens 
One in each Setmiecll, eee eese 82 
One in one semicell, two in the other ............ 38 
Two in each semieell ......................sssssssss 356 
Two in one semicell, three in the other ......... 24 
Three in each semicell.............................. s. | 5 
| | - 
500 
* Lütkemüller records this species as Docidium Baculum, Bréb, ; cfr. West 
& G. S. West in Journ. Bot, 1895, p. 65. 
t ‘Annals of Botany,’ vol. xii. March 1898, no, 45. 
