NATURE 



385 



THURSDAY, AUQUST 21, 1890. 



FRESHWATER ALG^. 

 Introduction to Freshwater Algce, with an Enumeration 

 of all the British Species. By M. C. Cooke, M.A., 

 LL.D., A.L.S. With 13 Plates. (London: Kegan 

 Paul, Trench, Triibner, and Co., Limited, 1890.) 

 p\R. COOKE is justified in saying, in his preface, that 

 A->' no apology is needed for the production of this 

 volume, the latest addition to the " International Scien- 

 tific Series." Notwithstanding the increased attention 

 which has been paid of recent years in this country to 

 this interesting and beautiful class of plants, we have had 

 hitherto no popular hand-book devoted to their structure 

 and their classification ; the only existing works on 

 British freshwater Algse, by Hassall, and by Dr. 

 Cooke himself, having been published at a price which 

 places them out of the reach of the great majority of 

 -collectors of Alga^. 



More than one-half of the present volume is occupied 

 by a general account of freshwater Algae, the main points 

 connected with their structure and modes of multiplica- 

 tion, and useful instructions as to their collection and 

 preservation. The greater part of this introductory por- 

 tion is very good, and will serve admirably to interest and 

 to instruct those who are turning their attention to the col- 

 lection and determination of the plant -denizens of our 

 streams and pools. In the chapters headed "Poly- 

 morphism," "Spontaneous Movements," and "Notable 

 Phenomena," a large mass of interesting information is 

 brought together, and the views of the leading authorities 

 well and clearly presented. In the chapter on " Conjuga- 

 tion," although the present writer naturally dissents from 

 Dr. Cooke's conclusion as to the nature of the process in 

 the Zygnemaceae, no objection can be taken (except on 

 one minor point) to the way in which both sides of the 

 controversy are presented. 



The last two chapters of the Introduction, " The Dual 

 Hypothesis," and "Classification," are much less satis- 

 factory. By the "dual hypothesis" is meant the theory 

 that Lichens are compound organisms made up of a 

 fungal and an algal constituent. Dr. Cooke is, of course, 

 perfectly at liberty to come to a different conclusion on 

 this subject from that of nearly all biologists who have 

 investigated it experimentally ; but, at least, if the hypo- 

 thesis is discussed, the arguments on both sides should 

 be fairly stated. The synthetical construction of a Lichen 

 out of its constituent elements has been affirmed by 

 authorities so worthy of respect as Stahl and Bonnier— a 

 fact which, if established, settles the question in a sense 

 opposite to that accepted by Dr. Cooke ; and yet these 

 observations are not even alluded to, much less contro- 

 verted, by him.i 



The chapter on Classification is chiefly occupied by 

 animadversions on a system different from that adopted 

 by the author, which has been proposed by other writers 

 on the same subject, "the most pretentious of philoso- 

 phical systems," which he treats with a certain amount 



« Martelli has quite recently recorded a complementary process in the 

 eStr" * (.Lecancra subfusca) into its algai and fungal 



NO. 1086, VOL. 42] 



of unphilosophical scorn. Any attempt to classify accord- 

 ing to their genetic affinities a class of plants about which 

 so much still remains to be learnt as our freshwater 

 Alg£e, must necessarily be to a large extent tentative ; 

 but we do not think that practical algologists will be 

 grateful to Dr. Cooke for perpetuating, as the basis of 

 his classification, the obsolete system of Rabenhorst's 

 "Flora Europaea Algarum aquas dulcis et submarine," 

 published in 1864, placing together, for example, Pabnella 

 and Apiocystis in one family, Protococcus and Pedi- 

 astrum in another family, and retaining, as a primary 

 group, the " Nematophyceas." From the sentence on p. 1 87, 

 the reader would suppose that the separation of the 

 Protophyta as a distinct class was a fad of the "con- 

 structors of paper systems," for whom he expresses so 

 great a contempt, instead of having the sanction of such 

 authorities as Luerssen and Sachs long before these 

 "paper systems" were published. 



The latter and smaller part of the work is occupied by 

 a description of the families and genera, and of all the 

 known British species, of freshwater Algs. Though not 

 so stated on the title-page, the two largest families, the 

 Desmids and Diatoms, are not included ; but this was 

 inevitable, to bring the work within moderate compass. 

 The Characeae, which also form a part of Hassall's 

 "Freshwater Algx," are likewise, and, as we think, 

 rightly, excluded. The plates include a drawing of 

 one species of each genus ; they are copied from the 

 plates in the author's " British Freshwater Algs," and 

 are not improved in the process. It is no fault of Dr. 

 Cooke's that with Algas, even more than with flowering 

 plants, it is often almost impossible to distinguish the 

 species from verbal descriptions only ; those given here are 

 mostly taken from the best writers, and could, on the whole, 

 scarcely be improved. Small inexactnesses in spelling 

 or in expression occur with irritating frequency— such as 

 " immovable " for " motionless " in describing the spores 

 of Chantransia, " Kutzing " (and Kutz.) throughout for 

 "Kiitzing," '' Bulbochoete" for '' Bulbochaete," " Glaeo- 

 cystis" for " Glceocystis," "cytioderm" for " cytoderm," 

 &c. ; but of more serious inaccuracies we have noticed 

 very few. We must, however, enter a word of protest 

 against the Glossary, taken, apparently, almost verbatim 

 from the author's " British Freshwater Algae." A good glos- 

 sary is an excellent thing ; a bad glossary is useless, or 

 worse. What are we to make of such definitions as the 

 following: "Antheridia, certain reproductive organs 

 supposed {sic) to be analogous to anthers, or fecun- 

 dative " ; " Carpospore, spores produced by conjugation 

 {sic) in a sporocarpium " ? Under the Chroococcacea 

 we find a constant reference to a mucous, gelatinous, 

 or crustaceous "thallus"; turning to the glossary, we 

 find a thallus to be " an expansion somewhat resembling 

 a leaf" ! " Trichogonia " are " the female reproductive 

 organs in Batrachosperms " ; under the Batracho- 

 spermeae we find no reference to any sexual organs 

 of reproduction. 



The work, as it stands, will be in the hands of every 

 collector and lover of Algae. If, in preparing a second 

 edition. Dr. Cooke will consent, in deference to the 

 views of other algologists, to re-write the two chapters in 

 his " Introduction " to which we have called attention, 



