Reviews and Book Notices. 159 



A Monograph of the British Desmidiacese, by W. West, F.L.S., 

 and G. S. West, iW.A., F.L.S,, A.R.C.S. \ol. III. Ray Society. 

 274 pp., 31 plates, price 25/- net. 



The third vohime of this useful work has appeared, and is devoted 

 •entirely to the genus Cosmarium, of which fifty species, and a number of 

 varieties were figured and described in the second volume. To these the 

 present volume adds 174 additional species, with a considerable number 

 of varieties. From some remarks in the introduction (\'ol. I.), in which 

 the authors suggested that the genus Cosmarinm might some day have to 

 be split up into smaller genera, one may infer that they feel this number 

 to be out of all proportion to its importance, and in this we are disposed 

 to agree, though we think there may be some difference of opinion as to 

 the suggested remedy. A careful examination of the descriptions and 

 plates of this genus does not encourage the idea of finding sound grounds 

 for generic differences, but rather suggests that even for specific and x^arietal 

 discrimination, the most has been made of some minute points of difference. 



The author says (page 128) ' We arc gradually arriving at the con- 

 viction that external form is the dominating factor in the determination 

 of the species groups in Desmids.' Along side this extract, we quote 

 from the description of Cosmaviuni regnesi (Plate 78) — ' the new semi- 

 cells regain the more pronounced character of the species after having 

 partially lost it by repeated divisions.' This appears to be an admission 

 that the external form is liable to mutation at different periods of its life 

 history. 



It is evident that every fresh form that is described as a new species 

 does, as a matter of fact, something to bridge over the differences between 

 certain other species, and as this process is continually going on, a time 

 will inevitably come when it will be necessary to recognise that the number 

 of real species is very limited, and that much simplification of the study 

 of this genus may be obtained by a judicious process of ' lumping.' 



But before this can be undertaken successfully, there remains much 

 work to be done in watching the growth and development of many of the 

 forms. In many cases we notice Messrs. West add the significant remark — 

 ■' Zygospore unknown.' Perhaps some of our local students of tiie fresh 

 w-ater AlgiP will take the hint, for in Yorkshire, notably in the moorland 

 ■districts of the West and North Ridings, we have a very considerable 

 Desmid Flora. 



Of the plates accompanying the present volume, it is sufficient to say 

 that they fully maintain the clearness and delicacy which are such marked 

 characteristics of the previous volumes. We notice nothing is said as 

 to any further issue, but, judging by the extent of ground already covered, 

 and the genera that have not yet been described, one may presume that 

 another volume (or perhaps two) will appear in due coui'se. R. H. P. 



We have received from Messrs. J. M. Dent & Co., the first part of 

 ' Trees and Shrubs of the British Isles, Native and Acclimatised,' by 

 C. S. Cooper and W. P. Westell, and coloured and ' black and white ' 

 plates from drawings by C. F. Newell. The work is to be completed in 

 sixteen parts at i/- net each. The frontispiece is a coloured representation 

 ■of the Strawberry tree ; and there are a number of ' black and white ' 

 plates, shewing the structures of leaves, etc. ; the drawing of some of which 

 might be improved. With each species is given a description of its dis- 

 tribution, flowers, leaves, etc. We cannot find any new features in the 

 work, but when complete, it will form a large, attractive and cheap \olume. 



We have received the Records of Meteorological Observations 

 taken at the Observatory, Edgbaston, 1908, by Alfred Cresswell. It is 

 issued by the Birmingham and Midland Institute Scientific Society, is 

 sold at two shillings ; and whilst it is not a pamphlet that will be read from 

 ■cover to cover, it certainly contains a very valuable record of systematic 

 observations. The pity is that similar publications are not issued from 

 many other districts. 



1909 April I. 



