68 UNIVERSALITY OF DEGENERATIVE EVOLUTION 



SECTION II. 

 Modification of the organs of plants. 



4. Modification of homodynamic organs in the 

 Individual. 



For the same reasons as we have already 

 pointed in the case of vertebrates, those leaves 



which grow out of 

 different parts of the 

 main stem, and have 

 undergone many 

 modifications in 

 order to adapt them- 

 selves to their vari- 

 ous functions, will 

 best serve as ex- 

 amples for our pre- 

 sent demonstration. 

 In descriptive 

 botanical treatises 

 the term "leaf" 



FIG. 37. Growing point of Vicia varia, 



showing the origin of leaves. 

 1, 2, 3, 4, leaves respectively older; leaf 1 is 

 still in the primordial condition ; leaf 2 is armlipH without, 

 divided into epipodium and hypopodium (h). d PP neu W11 



IS 



In leaves 3 and 4 the epipod is divided into 

 the hypopod forms 



petiole and leaflets, and 

 stipules. 



crimination. As a 

 rule, however, this 



term should only be applied to the true leaves, i.e. 



those of which the parts are fully developed 



throughout. 1 



1 The embryological development of the leaf among the Angio- 

 sperms (fig. 37) exhibits the following phases : The leaf arises 

 from the growing point in the form of a small bud, which grows 



