NOTICES OF NEW BOOKS. 389 



A Monograph of the British Lichens. A Descriptive Catalogue of 

 the Species in the Department of Botany, British Museum. Part I., 

 second edition. 519 pp., 71 pis. and 11 figs, in the text. Annie 

 Lorrain Smith, F.L.S., Acting Assistant, Department of Botany. 

 Printed by Order of the Trustees of the British Museum. 30s. net. 



This volume, as will be seen by the above, is described on the title- 

 page as Part I., second edition, but on turning to the preface one learns 

 that it is much more than a second edition, for it has been completely 

 re-written and re-arranged so that it forms an independent work 

 companion to Part II. by the same author, issued in 1911. 



Among the new features of this edition is an introduction to the 

 study of lichens, which gives a lucid and concise summary of the chief 

 points of our present-day knowledge of these plants. It is arranged 

 under the following sections : the lichen plant, morphology, reproductive 

 organs, physiology, ecology and distribution, phylogeny and classification. 



In the description of the lichen plant Miss Lorrain Smith states that 

 it is formed " from the union, in intimate symbiotic relationship, of two 

 separate plants, a fungus and an alga." This point of view appears to 

 accord more nearly with the facts of present-day knowledge than does 

 the theory of pure parasitism on the part of the fungus ; a theory which 

 is based to a large extent upon the penetration of the algal cell by the 

 fungus hypha. Such penetration, although figured and described in 

 text-books, cannot be claimed as the prevailing state of the relationship 

 between the fungus and the alga in the lichen thallus. In a large 

 number of British fruticose and foliose lichens penetration of the algal 

 cell by the hypha takes place seldom, if ever. The vast majority of 

 algal cells in a lichen thallus have the appearance of being perfectly 

 healthy, and the number of dead, or partially empty cells is, in many 

 species, exceedingly small. The algal cell of a lichen thallus can no 

 longer be regarded as influenced so profoundly by the fungus as to cause 

 it to lose its power of reproduction except in a vegetative manner, for at 

 certain seasons of the year great numbers of algal cells sporulate, and it 

 is by this means, and not by vegetative cell division, that the number of 

 algal cells (gonidia) is increased. The formation of spores with the 

 rapid development of these within the mother-cell into gonidia, is 

 similar to that observed in free Chlorella cells. 



We cannot agree with Bruce Fink, who has stated recently that the 

 theory of symbiotic relationship is " wrong." He has further asserted 

 that "in America, at least, and we believe in Europe as well, there has 

 been a marked recent trend of opinion among students of lower plants 

 to the effect that the dual hypothesis regarding lichens is untenable, 

 and that the lichen must be a fungus after all, parasitic on an alga." 



Bruce Fink has in no way justified this pronouncement, which, as 

 far as we know, is unsupported by lichenists in Europe, with the possible 

 exception of A. A. Elenkin and A. N. Danilov. The results of recent 

 research, as noted above, give no evidence in support of parasitism. 



The illustrations to the introductory matter represent highly 

 magnified sections of the thallus and apothecia of the lichen. These 

 illustrations bear evidence of the fact that field characters are not always 



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