CHAP, ii The Theory of Metamorphosis 67 



ind the study of them became greatly developed and ex- 

 tended after 1860. Naegeli himself never appears as a very 

 prominent supporter of the theory of metamorphosis, 

 ind his work of 1867, in conjunction with Schwendener, 

 .eads to criticisms which appear certainly as damaging to 

 the dogma, if not subversive of it in its earlier form. The 

 slight amount of differentiation of form recognizable in 

 the lowlier, if not in all, Thallophytes, was shown to be 

 net with also in the higher plants cases like Wolffia and 

 Lemna appearing among the Phanerogams. To describe 

 mch forms Naegeli and Schwendener introduced the term 

 hallome to designate the undifferentiated body of the 

 Diant. They suggested a further category of parts or 

 nembers, consisting of the hairs or outgrowths from the 

 general surface of either phyllome or caulome, to which 

 ;hey applied the name trichome. There thus stood out 

 'our categories of members which were considered co-ordi- 

 late, thallome, caulome, phyllome, and trichome. 



These suggestions of Naegeli and Schwendener, though 

 :hey seem at first sight only to make the morphological 

 :onception of the plant comprehensive and complete, are 

 'ound on examination to be antagonistic to the theory 

 )f metamorphosis, as propounded by Wolff and Goethe. 

 Fhe conception of the thallome implies that the differentia- 

 ion of the plant body into leaf and axis is not fundamen- 

 :al. It is agreed on all hands that the archegoniate plants 

 lave been derived or evolved from the lowlier forms 

 ind as at any rate the simpler of these hardly show a 

 lifference between stem and leaf, such difference must 

 lave been acquired during the course of development. 

 !f so, a differentiated stem and leaf cannot form the founda- 

 ion on which the form of the plant-body has depended, 

 ^rom the point of view of those who do not accept the 

 position of Wolff the course adopted by Naegeli does not 

 10 much solve as evade the difficulty of bringing the theory 



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