CHAP, ii The Theory of Metamorphosis 67 



and 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, 

 and his work of 1867, in conjunction with Schwendener, 

 leads 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 

 met with also in the higher plants cases like Wolffia and 

 L&mna appearing among the Phanerogams. To describe 

 such forms Naegeli and Schwendener introduced the term 

 thallome to designate the undifferentiated body of the 

 plant. They suggested a further category of parts or 

 members, consisting of the hairs or outgrowths from the 

 general surface of either phyllome or caulome, to which 

 they applied the name trichome. There thus stood out 

 four categories of members which were considered co-ordi- 

 nate, thallome, caulome, phyllome, and trichome. 



These suggestions of Naegeli and Schwendener, though 

 they seem at first sight only to make the morphological 

 conception of the plant comprehensive and complete, are 

 found on examination to be antagonistic to the theory 

 of metamorphosis, as propounded by Wolff and Goethe, 

 The conception of the thallome implies that the differentia- 

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

 tal. It is agreed on all hands that the archegoniate plants 

 have been derived or evolved from the lowlier forms 

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

 difference between stem and leaf, such difference must 

 have been acquired during the course of development. 

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

 tion on which the form of the plant-body has depended. 

 From the point of view of those who do not accept the 

 position of Wolff the course adopted by Naegeli does not 

 so much solve as evade the difficulty of bringing the theory 



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