10 



vegetative development in its changes. The cases cited indicate 

 that there is a " vast independence of generative maturity and 

 vegetative growth. Of course a definite ' nutrition-minimum ' is 

 absolutely necessary. Beyond this, the way for generative ma- 

 turity, flowering {Die Blutenreife), arises independently. Every 

 favoring constellation is able to induce it, even though vegetative 

 development be insignificant, and though the age be juvenile. 

 Practically, all cases of ' early blooming,' or on the other hand 

 of ' nanism,' signify how flowering is favored ' by dryness or by 

 the disturbance of the nutrition conducive to growth.' " 



In Chapter III, " HclikouiorpJiic unci Blutenreife bei lieteroblas- 

 tischen Pflanzen,'' the author refers to Goebel's classification of 

 development into " heteroblastic," where the differences between 

 the configuration of the plant at different stages in its vegetative 

 development are very small, and " homoblastic," where these 

 differences are large. Goebel, in his "Organography," has 

 already pointed out that no sharp line can be drawn between 

 homoblasts and heteroblasts. Juvenile forms [Jugendfonnen) 

 and subsequent forms {Folgeformeii) have been recognized. Diels 

 proposes to apply to both the general term " helikomorph." " I 

 call a form a ' liclikoniorpJi' " he says, "which appears at a defi- 

 nite phase of vegetative development, that is, at a definite (rela- 

 tive) age(Gr. j/.r/ca = Sige)." The term signifies, in general, the 

 vegetative configuration dependent upon the phase or age. 



Helikomorphs are classed as: i. Heteroblasts with arrested 

 primary leaves ; 2. Heteroblasts with arrested subsequent leaves 

 {Folgebldtteni) ; 3. Heteroblasts with helikomorphs of Indeter- 

 minate characters. The greater portion of the book (pp. 23-108) 

 is occupied with illustrations of the various classes, under the 

 subheads, {a) cases conditioned by external conditions {exogeiier 

 BedingtJieit), including seasonal dimorphism ; {b) cases whose 

 conditions are unknown. 



The phylogenetic significance of helikomorphs is discussed in 

 Chapter IV. " After the attainment of a certain minimum of 

 vegetative preparation, flowering can occur in very diverse phases 

 of development and bring about the termination of vegetative 

 unfolding." 



