4 



PRINCIPLES OF PLANT-TERATOLOGY. 



method is of subsidiary value for determining the 

 morphological nature of an organ. 



Thirdly, we have the comparative method, which is 

 pre-eminently serviceable, for a structure, the nature 

 of which is obscure in a particular species, can often 

 be elucidated by comparison with the appearance 

 which it presents in an allied species or genus. 



Fourthly, and surely most important and valuable 

 of all, is the teratological method. In very many cases 

 the so-called " freaks " and " monstrosities " represent 

 reversions or harkings-back, in one form or another, 

 to an ancestral condition, but this will always take 

 place in a way which is modified by the structure and 

 idiosyncrasies of the organ which is undergoing 

 change. For example, a vegetatively proliferated 

 rose, whose floral organs change into green leaves 

 and become vertically displaced owing to elongation 

 of the floral axis, tells us better than the facts of its 

 ontogeny would, better than those of its anatomical 

 structure, better even than would any comparison 

 of the flower in its normal state with any other type 

 of flower, that the flower has been derived in the 

 past by congestion and abbreviation of an axis, and by 

 the extreme reduction and modification of leafy sporo- 

 phylls. But it would be absurd to suppose that the 

 leafy shoots from which our flowers originally sprang 

 in any sense resembled, save in the matter of possess- 

 ing an elongated axis and leafy sporophylls, those into 

 which our modern flowers so frequently proliferate. 

 Under special conditions of nutriment and moisture, 

 the older tendency to break the bounds which an 

 adaptive evolution has placed upon the flower becomes 

 manifested. This is a very different view from that 

 which regards the proliferation as a mere haphazard 

 and meaningless occurrence. 



But floral proliferation is not nearly so instructive 

 and so full of meaning in connection with the ancestry 

 and morphological nature of the parts concerned as 

 are certain other abnormalities such as those occasion- 



