ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 415 



have aerial roots or roots which reach the soil ; or they form themselves 

 a matrix of decaying animal and vegetable matter. Some epiphytes, but 

 exclusively those found on the lower branches of trees, grow also on 

 rocks. The largest number of epiphytic plants are found on the 

 arboreal vegetation of mountain slopes in tropical and subtropical 

 climates. 



Influence of Alpine Climate on Vegetation.* — M. G. Bonnier 

 describes certain experiments on the cultivation of plants at various 

 altitudes. His ganeral conclusion is, that, under the same atmospheric 

 conditions, the leaves of plants growing at high altitudes liberate more 

 oxygen than do those growing at lower levels. 



Parallel Forms.f — Herr F. Krasan attempts to trace the mode of 

 genesis of one species out of another, and of parallel forms of different 

 species under similar external conditions. He regards variability as 

 not induced by the physical influence of the soil, but as independent of 

 external factors. The environment can only give rise to tendencies 

 which transform the possibilities already in the plant into actual meta- 

 morphoses. In order to produce positive results by cultivation, it is 

 necessary to make use of observations and experiments on living plants 

 conducted through a number of years ; and only those forms are adapted 

 to this which belong to notoriously variable types. 



B. CRYPTOGAMIA. 



Bennett and Murray's Cryptogamic Botany, f — We heartily con- 

 gratulate the authors on the publication of this book. Following in the 

 wake of Vines's 'Physiology,' Bower's 'Practical Botany,' and the 'Annals 

 of Botany,' it is a healthy sign that the British school has successfully 

 cast off its German moorings. Nothing of the kind " has appeared in 

 the English language since the Eev. M. J. Berkeley's in 1857." " The 

 aim of the authors has been to bring before the reader the main facts of 

 structure, of development, and of life-history, which mark the larger 

 groups," with reference " only to the broader lines of demarcation." By 

 the attention they have paid to the fossil remains, by the numerous illus- 

 trations, and precise terminology, they have succeeded in producing a 

 singularly clear and readable handbook. 



The plan of dealing with the subject is a descent from the higher 

 to the lower types, arranged in seven subdivisions. 



Subdivision I. (Vascular Cryptogams) occupies about one-quarter of 

 the book, and concludes with an admirable account of several fossil forms. 

 Then follow the Muscinese (Subdivision II.). The Characege (Subdivision 

 III.) are considered to be a distinctly higher type than the Thallophytes. 

 The Algse constitute the fourth subdivision, and occupy another quarter 

 of the book. About 100 pages are devoted to a treatment of the Fungi 

 (Subdivision V.) which forms an excellent introduction to De Bary's 

 'Comparative Morphology and Biology of the Fungi, Mycetozoa, and 

 Bacteria.' Subdivision VI. deals with the Myxomycetes and Acrasiae, 

 which are so closely linked with the Amoebae that they are regarded as 



* Bull. Soc. Bot. France, xxxv. (1888) pp. 436-9. 



t Oesterr. Bot. Zeitschr., xxxviii. (1888) pp. 192-9, 232-7, 293-5, 837-40. 

 X 'A Handbook of Cryptogamic Botany, by Alfred W. Bennett and George 

 Murray,' Svo, London, 1889, pp. viii, and 473, 378 figs. 



