CURRENT LITERATURE 



BOOK REVIEWS 



Form and flowering 



An interesting discussion of the relations between the vegetative form and the 

 flowering perio<I of plants is presented by Dr. DiELS in a small book,' issued 

 more than a year ago, which deserves notice in spite of unavoidable delay." 



The questions with which the book de^ were raised by the author's travels 

 in West Australia in igo2. After his return he examined the literature and made 

 further investigations to throw light upon the problems of form in the plant kingdom. 

 He has gather^ together a considerable number of examples of the relation 

 between form, blooming time, and external conditions. These he presents and 

 discusses in his usual luminous fashion. He has even cited briefly analogous 

 phenomena, not a few from the animal kingdom. 



The thesis of the book is that the generative maturity of plants is not connected 

 immutably with a definitive stage of their development, as has been so widely 

 held. A certain minimum of nutritive preparation is presupposed; but once 

 this is passed there is a broad variation zone in which blooming occurs. Its 

 appearance is dependent upon complex, largely unknown conditions, an important 

 part of which, however, are external. The vegetative ontogeny depends upon 

 the cooperation of autogenous and exogenous (an excellent substitute for the 

 awkward term "aitiogenous") factors; for the rudiments of the vegetative oipns 

 have many possibilities, and which one is realized is determined by the environ- 

 ment. The mature form of the entire organism is thus a product of vegetative 

 ontogeny and of generative maturity, both of which factors are variable, though 

 theu- variabUity is not in the same direction. True, the development of vegetative 

 structures usually ceases at blooming, but this is the only place where the two lines 

 of development, the vegetative and the generative, are inseparably connected. 

 Elsewhere they are free and independent of one another and each varies after iU 

 own manner. In this connection of two variable factors lies an important impulse 

 to increase the manifold forms of the plant world. For the conditions which help 

 to regulate the succession of leaf forms and floral maturity change with the changes 

 of climate in space and in time, giving rise to local geographic species and aHowing 

 true species to arise in the course of time. Their features attain heritabiiity- and 

 become therewith a soiu-ce of new lines with new possibilities. 



I DiELS, L., Jugendformen und Bliitenreife im' Pflanzenreich. 8vo. pp. 130- 

 ^gs. ^. Berlin: Gebriider Borntraeger. 1906. M 3.80. 



» Hie work was sent to a reviewer on its receipt, and wa5 recently returned at our 



request. — Eds. 



