88 ORGANOGRAPHY. BOOK I. 



essentially distinct organs ; but, since the appearance of an 

 admirable treatise by Goethe in 1790, On the Metamorphoses 

 of Plants, proofs of their being merely modifications of one 

 common type, the leaf, have been gradually discovered ; so that 

 that which, forty years ago, was considered as the romance of 

 a poet, is now universally acknowledged to be an indisputable 

 truth. It may, however, be remarked, that when those who 

 first seized upon the important but neglected facts out of 

 which this theoiy has been constructed, asserted that all ap- 

 pendages of the axis of a plant are metamorphosed leaves, 

 more certainly was stated than the evidence would justify ; 

 for we cannot say that an organ is a metamorphosed leaf, when, 

 in point of fact, it has never been a leaf. What was meant, and 

 that which is supported by the most conclusive evidence, is, 

 that every appendage of the axis is originally constructed of the 

 same elements, arranged upon a common plan, and varying in 

 their manner of developement, not on account of any original 

 difference in structure, but on account of especial, local, and 

 predisposing causes : of this the leaf is taken" as the type, 

 because it is the organ which is most usually the result of the 

 developement of those elements, — is that to which the other 

 organs generally revert, when, from any accidental disturbing 

 cause, they do not sustain the appearance to which they were 

 originally predisposed, — and moreover, is that in which we 

 have the most complete state of organization. 



It is not my intention to enter into nuich separate discussion 

 of this doctrine; proof of it will be more conveniently ad- 

 duced as the different modifications of the appendages of the 

 axis come separately under consideration. The leaf, as the 

 first that is formed, the most perfect of them all, and that 

 which is most constantly pi'esent, is properly considered the 

 type from which all the others are deviations, and is that 

 with the structure of which it is first necessary to become 

 acquainted. 



