METAMORPHOSIS IN PLANTS. 101 



We see that, in spite of the differences of opinion as to 

 the precise mode in which it takes place, modern Botany 

 has established the doctrine of material metamorphosis 

 upon a sound basis of observed fact ; and in arriving at this 

 result I have accomplished one of the chief objects of this 

 lecture. I will, however, venture to trespass on your 

 patience for a few minutes longer to briefly consider in con- 

 clusion some of the theories which have been propounded 

 for the purpose of explaining the occurrence of meta- 

 morphosis. 



It is easy to account for the various metamorphoses of 

 the members of the plant on the metaphysical principle of 

 final causes, by simply asserting that any given meta- 

 morphosis is to the advantage of the plant — for instance, that 

 the metamorphosis which results in the production of petals 

 is to be attributed to the advantage gained by the plant in 

 the cross-pollination by means of insects which the brightly 

 coloured petals ensure — and, no doubt, as far as it goes, this 

 explanation is sound. But I desire to lead you farther than 

 this, and to inquire on the physical method whether or not 

 some efficient cause may be found ; and, if so, what the 

 nature of the efficient cause or causes may be. 



Some light will be thrown on this difficult matter by the 

 consideration of metamorphoses, which we may distinguish 

 as traumatic, caused by the attacks of insects and other 

 parasites. It is known that chloranthy, a condition in 

 which all or the great majority of the floral organs assume 

 the form and colour of foliage-leaves, is frequently induced 

 as the result of puncture by insects or by the growth of 

 fungi in the tissues 1 . Here then is a case of metamorphosis 

 which can be clearly traced to an efficient cause ; but we 

 must endeavour to penetrate farther into the matter and 

 ascertain as far as may be the mode in which the attacks of 

 these parasites bring about so striking a change. 



Flowers, " Nature Series," 1882. His point of view is, however, somewhat 

 different from that stated above, in that he assumes that " The starting- 

 point consists of a plant having three kinds of organs, true foliage-leaves, 

 staminal leaves and carpellary leaves" (p. 14). 



1 Masters, Vegetable Teratology, 1869, 279 (Ray Society). 



