BRITISH FRESHWATER ALG 387 
regards their sexual reproduction, than the majority of the Desmids, 
and there seems - ae no evidence that the sexual process of the 
latter i am eo 
study of t s gr ae The systematic portion of the book, which 
eoadee a ecahar of new forms, has been very carefully worked 
; the descriptions of genera, species, and varieties, are ample, 
whilst the range of each species in Britain and throughout the 
printed in large, clear type, and the excellence of the plates has 
already been sufficiently commented u upon 
Prof. George West is to be warmly song rhb idial for issuing so 
ey useful a book as the T'reatise on British Freshwater Algae 
is likely to be; and the want, so keeuly felt in this country, for a 
book of this kind, has been satisfied in an adequate manner. Prof. 
the 
eb features of the book. It is to be regretted that he did not 
e his way towards the inclusion of the Per idinea, which certainly 
have several striking points in common with the Diatoms, although 
it gyal be granted that they diverge very widely from other groups 
of Alg The omission the Characee scarcely calls for remark, 
as choy appear to occup ery specialised Lae in the vegetable 
kingdom. A book, dealing with Freshwater Algz only, of course 
involves an artificial separation, but, ri en! the fact that the 
main groups of Algew dominant in fres water are only feebly repre- 
sented in the sea, any book dealing with the algal flora of a par- 
ticular region must necessarily only contain a certain percentage 
of all the forms of Alge known; why then should such a treatise 
not be further delimited, and be confined to the consideration of 
those forms, which inhabit fresh water ? Bie h a delimitation is 
less artificial than the purely geographical o 
The first thirty-three pages of the at Ge are devoted to general 
considerations, including useful information as to the occurrence, 
collection, preservation, ‘and cue tion of Freshwater Algw, whilst 
the general discussion 0 olymorphism of this group may be 
bs Sins from some that ae of steen Algee (a ca sible vite 
e 
Conjugate would be better treated apart from them, as Wille does. 
The group of the Hetervkonte, established by paths is made use 
of to include a number of green forms, which, in addition to other 
peculiarities, sonia abundant xanthophyll in their Pia Beh ars 
