5o 
Review. 
not unknown in the Protococcales ( e.g . in Asterococcus ) and are 
not there regarded as of marked taxonomic value. 
Brief attention may be given to certain other points in the 
arrangement of the Isokontae. Sphcerella and Stephanosphcera 
are separated from the Volvoeaceae, as the Sphserellaceae, a 
change which appears quite warranted. The subdivision of the 
palmelloid Protococcales into Chlorangieae, Palmelleae, Tetras- 
poreae, Palmophylleae, and Gloeocysteae brings out clearly the 
affinities of the different forms, but we should have preferred to 
include also the Dictyosphaeriaceae which the author regards as a 
separate family. We doubt the advisibility of placing Protococcus 
(the name now adopted for Pleurococcus) in the same family 
(Protococcaceae) as Trochiscia and Chlorella, since the method of 
propagation in the former is mainly by vegetative division, which 
is not encountered in the other two genera; there also appears to 
be certain differences in the chloroplasts. The position of 
Pleurococcus is of course still very obscure, and this is partly owing 
to incomplete discrimination between the species of this genus and 
those of Chlorella, Chlorococcum (which the author now recognises 
as an independent genus, cf. p. 209), and Chlorosphcera, but the 
present writer is much inclined to adopt the view propounded by 
some algologists that Pleurococcus is a reduced member of Chaeto¬ 
phoraceae. In any case he is not disposed to agree that the species 
of Chlorosphcera “are the relics of intermediate forms between 
Protoccccus and the lowest form, viz. Chlorococcum, of the Chloro- 
chytrieae ” (p. 195). Chlorosphcera is certainly allied to the latter, 
but we doubt if it is to the former. The inclusion of Chcetopeltis, 
Chcetosphceridium, etc., in the Protococcales (family Chaetopel- 
tidaceae) may be justified, although here also we are possibly 
dealing with reduced Chaetophoraceae. It may be doubted whether 
all the genera comprised in Chaetopeltidaceae really form a natural 
group. The suggestion that Endosphcera, Scotinosphcera,Chlorocystis, 
Stomatochytrium, and Centrosphcera (cf. p. 454) be merged in the 
genus Chlorochytrium will probably find whole-hearted approval 
from most algologists. 
In his treatment of the Siphonales (in which Vaucheria and 
Dichotomosiphon are rightly included) Halicystis is placed together 
with Protosiphon in the family Protosiphonaceae. We are fully in 
agreement with this step, in fact we think the scope of the 
Protosiphonaceae might with advantage be still further enlarged. 
We are glad to find that the author now includes Protoderma in 
the Chaetophoraceae and that Rhaphidonema is recognised as an 
independent genus, although it would perhaps be better referred to 
Chaetophoraceae than to Ulotrichaceae. 
As regards the classification of the Heterokontae the merging 
of Pascher’s Heterochloridales, Heterocapsales, and Heterococcales 
in one order is open to criticism, as also the inclusion of forms like 
Chlorosaccus, Mischococcus, and Stipitococcus in one family. 
Two phylogenetic points call for special consideration. The 
author follows Blackman and Tansley and others in deriving the 
Ulotrichales from the palmelloid Tetrasporineae (cf. pp. 158, 281). 
It may be that this view is justified, although there is little direct 
evidence, but we think that Oltmanns’ suggestion as to a possible 
