105 
cells on specimens, communicated by Bréb., mani¬ 
fested it as a Pleiirotcenium Næg. 
The only original figure of Docidium Baculum^ 
showing the structure of the chloroplast, is the one 
in Ralfs Brir,. Desm. (and perhaps Rabenhorst’s 
figg.). The figures 12—16 in Delponte Desm. 
subalp. t. 20 belong to Bleurotœnium, as also his 
description p. 226 shows: ”Endochroma formato da 
pill lamine di clorophilla parietali diretta, con globetti 
di fecola sparsi, ma senza traccia dei globoli grossi, 
disposti in serie, accennati dal Ralfs. Spazi vesicolari 
alle due estremita distinti, privi dei pun ti sugli orli 
della sutur a , figurati dal Ralfs”; any basal plications 
are not to be seen on the figures. — According to 
West, 1895, Lütkemüller’s figg. in Chlorophyll- 
körp. ein. Desm., 1893, t. 2 f. 9 —15 belong to 
Benium minutum^ in which the chloroplastes are ”vari¬ 
able” (cfr West Brit. Desm. 1). 
Therefore it seems to me most advisable to follow 
the practice of keeping Docidium in Ralfs Brit. 
Desm. collective, and, when it is divided, then to take 
it in the sense of Lunde 11, leaving all the other 
species to Pleur otcenium. 
The genus Penium was first mentioned by Bre- 
bisson in 1844 (Diet. univ. hist. nat. 4), who con¬ 
stituted it for Cylindrocystis Brébissonii, established 
by Meneghini 1838 on ^Palmella cylindrospora Bréb. 
ined.” (already described in 1835 in Alg. Pal.), and 
gave it the name Penium palangula^ after having 
demonstrated copulation on it. This desmid is very 
presumably not identical with Cosmarium palangula 
Bréb. 1848 (as I had supposed in Ind. Desm.) or 
Brébisson had confounded them. Even Kuntze 1898 
regarded Penium Bréb. 1844 as another genus than 
Penium Kütz. ”Bréb.” 1849. 
Ralfs said in Brit. Desm. that Brébisson then 
considered Cylindroeystis Menegh. as a proper genus. 
