386 THE JOURNAL OF BOTANY 
NOTICES OF BOOKS. 
British Fresuwater ALG. 
A Monograph of the British Desmidiacee. By W. & G. S. West. 
ol. I. Pp. xxxvi, 224. With 82 plates. London: the Ray 
Society, 1904. Price 25s. net. 
A Treatise on the British Freshwater Alga. By G.S. Wxst. Pp. xv, 
372. With 166 figures in the text and one plate. Cam- 
bridge University Press, 1904. Price 10s. 6d. net. 
Since the time of Ralfs’s British Desmidiee, and Cooke’s rather 
incomplete work on the same subject, no attempt has been made to 
put together all that is known about the British representatives of 
this beautiful group of Alge. The name of West, on the title- 
page of this new work, is in itself an assurance that the attempt 
has been undertaken by those well qualified to carry it out success- 
> 
aspects. The descriptions of the plates are conveniently placed, 
us pores 1 e cell-wall, and the mucilage which is ex- 
ereted from them, are only briefly touched upon, although they 
have been shown t ry considerably in structure in different 
they should be; some notice of Schroeder's recent work on the 
movements of Closterium and Euastrum by exeretion of a mucila- 
ginous stalk would not have been out of place. The mode of divi- 
sion of a Desmid is not quite clearly described in all details. The 
ment that ‘‘ changes in the conditions of environ ailect 
the characters of a species unless they act for a long period of time. 
This remark is a little vague, and does not exactly agree with current 
ideas of v o e Desmidiacee are regarded ‘as a degenera 
family of unicellular Alge evolved by retrogression from sexually 
differentiated, filamentous Conjugates,” a which has already 
previously been expressed by the authors; this theory has never 
appeale us our opinion a arguments brought 
forward in its favour might just as well be reversed and made use 
‘of to prove the opposite. The filamentous Conjugates of the 
present day are certainly on a higher stage of differentiation, as 
