ON METAMORPHOSIS IN PLANTS. 



EVERY one who is specially concerned with vegetable 

 morphology at once recognises the important in- 

 fluence which the doctrine of metamorphosis exercises on 

 this branch of botany. 



By the metamorphosis, we express the perception that 

 the marvellous variety in external form exhibited by plants 

 is to be traced back to the diverse modifications of a very 

 few fundamental types. Furthermore, it may also be 

 pointed out that the study of metamorphosis is very closely 

 bound up with that of adaptation, and indeed one may 

 almost assert that a metamorphosed structure owes its 

 existence to an adaptive modification of a relatively primi- 

 tive type form. But as adaptations exhibiting" identical 

 characters may originate from different morphological 

 sources, we realise that the function of an organ need not 

 necessarily afford any clue to its real morphological nature. 

 In dealing with the progress which has been made in this 

 held of inquiry within recent years, it is not my intention 

 merely to discuss a number of particular instances in which 

 perchance the morphological characters have become more 

 clearly apprehended than formerly. What we are here 

 concerned with is rather the larger question of the general 

 aspect of the subject before us. 



And foremost amongst recent advances must be reckoned 

 that change of front which has led to an abandoning of the 

 attempt to refer to the reproductive organs, in the higher 

 plants, as if they were actually modified vegetative structures. 

 Formerly much controversy turned on the question as to 

 whether a sporangium or an ovule should be considered as 

 a modified hair (Trichome), or whether it should rank as a 

 foliar (Phyllome) or axial (Caulome) structure. At the 

 present time it is regarded as immaterial whether it corre- 

 sponds in position with any one of these organs; its essential 

 importance is discerned in its spore-producing character, 

 that is, ultimately, its functional property. And spore- 



