. ii The Theory of Metamorpliosis 79 



.eaf-bearing axes are not to be found. It is therefore 

 i matter of convenience where the boundary-line is drawn ' ; 

 ind again, ' The expressions thallome, caulome, phyllome, 

 trichome, root, designate, as has been said, several ideas V 



The development of the idea of metamorphosis, taken 

 n the sense in which Sachs used it, itself proceeded on the 

 ines of adaptation. Its most eminent exponent was Goebel, 

 who may in many respects be looked upon as Sachs' 

 successor. It was, as interpreted by him, fundamentally 

 norphological rather than physiological, though it recog- 

 lized the direct influence of the environment as a factor 

 n determining form. Writing in 1895, Goebel interpreted 

 netamorphosis as implying the perception that the variety 

 n external form exhibited by plants is to be traced back 

 :o the diverse modifications of a very few fundamental 

 ;ypes. He said that its study is very closely bound up 

 ,vith that of adaptation, and it might almost be asserted 

 :hat a metamorphosed structure owes its existence to an 

 idaptive modification of a relatively primitive type form. 



Goebel admitted that in certain cases it is not possible 

 :o differentiate the members of the plant definitely into 

 eaf stem root, but he opposed the idea that this negatives 

 :he metamorphosis of one of these into another or of 

 netamorphosis within the limits of each category. He set 

 )ut with fairness the impossibility of drawing a definite 

 ine of demarcation in all cases between leaf and stem, 

 nstancing the various shoot-like members of certain species 

 )f Ulricularia, which he claimed to have the morphological 

 /alue of leaves. He held, however, that though such a 

 lefinite separation of the two, of universal application, 

 :annot be found, yet such becomes practicable when we 

 imit our consideration to single groups of tolerably closely 

 illied forms, and that this is sufficient for the purpose of 

 .he theory of metamorphosis. The leaf and shoot rudi- 

 1 The italics are the Author's. 



