MINOR NOTES I 63 



An hitercsthi;^ hook by D'lels ( i ) has for its general 

 topic the relation hetween the \egetati\e and sexual func- 

 tions in the Howering plants. After summarizing our knowl- 

 edge of the conditions effecting reproduction in these forms, 

 he points out that hetween the higher and lower plants there 

 is no important difference in the condition inciting sexual 

 reproduction, anil in the Howering plants both the time and 

 the stage of de\elopment at which sexual reproduction occurs 

 is conditioned by external influences. Sexual maturity in the 

 Howering plants, Diels maintains, is, contrary to common 

 belief, independent of the vegetative stages which these plants 

 usually pass through. Necessarily a certain minimum of 

 vegetative structure is necessarv (perhaps for hierely 

 mechanical reasons) before the generative parts are pro- 

 duced, but that this is much less than is usually considered 

 the numerous examples w^hich the author brings together 

 clearly show. Diels follow^s Goebel in the use of the terms 

 "homoblastic" anci "heteroblastic" to distinguish between 

 those cases in which the progressive stages in the develop- 

 ment of the individual differ but slightly and those in which 

 the stages are more or even quite distinct from each other, 

 and introduces the new term "helicomorpmy" to include Goe- 

 bel's two terms "juvenile forms" and "successive forms" in 

 heteroblastic plants. 



The bulk of the book is devoted to a discussion of the 

 relation betwen helicomorphy and generative maturity in 

 heteroblastic plants. A wealth of illustrative material is 

 presented and there seems good evidence for the authors con- 

 tention that Howering far from being the terminus of heter- 

 oblastic development may be induced at any stage. 



A chapter is gi\en o\er to a discussion of the phylo- 

 genetic significance of helicomorphy which the author con- 

 siders as without \alue. Discussing the "biogenetic law," 



(1) Jugendfonn uiul Jllutcnreife in Pflanzenieich, Von. Dr. L. Diels, 

 Fnb. O. Gebriiedor BointriU'Kor. Berlin. 



