158 ORGANIC METAMORPHOSIS OF LEAVES 



mately, the branches cease to elongate altogether, and the 

 leaf-buds become metamorphosed into flower-buds. "When 

 these flower-buds unfold themselves, they disclose a number 

 of leaves totally different in appearance from the ordinary 

 stem-leaves, — certain changes having been made in their 

 structure by which they are adapted for reproduction. 



As in the flower, the vegetative powers of the leaves are 

 reduced to zero, the axis of the floral leaves necessarily 

 retains its rudimentary condition, and no intervals of stem 

 form between them ; they therefore remain crowded 

 together into a sort of rosette, analogous to that which is 

 formed by the ordinary stem-leaves, which remain in 

 clusters without metamorphosis when the branch or axis 

 to which they are attached continues undeveloped. 



If we examine the leaves which have been thus converted 

 into floral organs, we shall soon be satisfled that, despite 

 of the various forms under which they present themselves, 

 they are identical with the ordinary stem-leaves, and that 

 the alteration in their appearance is the necessary conse- 

 quence of the .gradual expiration of the vegetative powers 

 of the branch on which they are borne. 



In many plants,-^those with axillary inflorescences, 

 as, for example, the moth mullein ( Verbascum blattarid), 

 where the primary axis remains permanently vegetative, 

 and where the buds formed in the axilla of the upper 

 leaves are metamorphosed into flower-buds, the passage of 

 the ordinary green leaves of the stem into bracts or floral 

 leaves, is so gradual, that it is impossible to distinguish be- 

 tween the bract and the leaf; and, in like manner, the 

 bracts slide, as it were, almost imperceptibly into the 

 sepals or leaves of the calyx. In such cases, there is no 

 difficulty in verifying the fact, that leaf, bract, and sepal, are 

 one and the same organ ; for we plainly see how the leaves 

 diminish in size as we pass from the vegetative to the re- 

 productive region, and the successive steps made in the 

 metamorphoses of the ordinary green leaves of the stem 

 into the sepals or leaves of the calyx or flower-cup. 



But in cases where the inflorescence is terminal, that is 



