458 GRUNDRISS DER ENTWICKELUNGSMECHANIK. 



It may be noted by British botanists that the variety atro- 

 purpurascens of subsp. sublilacina was received from the Cambridge 

 Botanic Garden. Subsp. patens Wittr. has much the same habit as 

 V. aijrestis Jordan; tlie peduncles, however, are generally longer 

 than the leaves. Subsp. curtisepala Wittr. connects V. tricolor and 

 V. arvensis : it is related in certainly some of its characters to 

 V. (jracilescens Jord. ; and the last subspecies, striolata Wittr., has a 

 flower of about the same size as V. pallescens Jord., but the petals 

 are longitudinally striated. 



Viola olpestris (DC.) Wittr. occupies an intermediate position 

 between V. tricolor and V. arvensis. It is generally perennial, and 

 the flowers yellow or sulphur-coloured. It inhabits alpine or sub- 

 alpine situations ; and here are probably to be referred several of the 

 species described by M. Jordan from the Pyrenean region. Sub- 

 species suharvensis of this species was grown from seed received from 

 the Botanic Garden at Cambridge. 



Supplementary descriptions of the other species of the Melanium 

 section, previously mentioned, are also given, and there are many 

 other points of interest which cannot be dealt with in a brief notice. 

 No student of these plants can afford to ignore Dr. Wittrock's paper. 



E. G. B. 



Grundriss der Entwickelungsmechanik. By Wilhelm Haacke. 8vo, 

 pp. xii, 398, with 143 figures in the text. Leipzig: Georgi. 

 1897. Price 12s. 



This book, " the first work of its kind," is, the author explains, a 

 "Lehrbuch" in the original sense of the word, and does not aspire 

 to the rank of a "Handbuch." It is written with the object of 

 arousing to an interest in the science of "Entwickelungsmechanik" 

 all students of the physical and natural sciences and of their appli- 

 cations, and to acquaint them with its present position. Also the 

 full-fledged "Entwickelungsmechaniker" will find something new, 

 or at least suggestive, for the book partakes of the nature of an 

 investigation. 



He who has time and opportunity for reading the six chapters 

 into which the subject-matter is divided will find much that is 

 suggestive from the points of view of general biology and of botany 

 in particular, and will, if possible, be more fully convinced than 

 before that of making of books there is no end. In the first chapter, 

 "Voni Gebiete der EntwickelungsmechaniU," the author discusses 

 the possibility and defines the object of his science. Its task is to 

 investigate the part played by mechanical principles in the origin 

 and change of organisms. Assuming its existence, the writer deals 

 successively with its relation to Teleology, Vitalism, and Biology. 

 Early in the second chapter, " Vom Organismeusystem," under the 

 heading Rationelle Systematik we encounter the equation ax'^-\-bxy 

 -\-cy^-\-dx-\-ey-\-f=0. We do not wish to dispute the accuracy 

 of this statement, but, as it seems to have little or no bearing on 

 botany, we will pass on. Leaving behind pictures of crystals, a 

 diagrammatic transverse section of a fish, and the like, we come to 



