CHAP, i The Theory of Metamorphosis 81 



becomes actually transformed into another that meta- 

 morphosis is real and not a mere modification of the course 

 of potential development. He said, ' The primordia of the 

 organs at the vegetative point are not of an indifferent 

 nature, and do not consist of embryonal tissue capable of 

 developing in any direction. . . . We must assume for the 

 primordia of leaves the possession from their outset of 

 a definite, not an indifferent, material nature, which con- 

 ditions their further development.' He went on to argue 

 that the fate of a primordium may be entirely changed 

 by altering conditions ' If now all the foliage leaves be 

 removed from a plant of Onoclea, the development of 

 sporophylls is hindered the primordia of the sporophylls, 

 which are nothing else than primordia of foliage leaves, 

 are then forced to develop into foliage leaves and the 

 production of sporangia is either partially or entirely sup- 

 pressed'. 



Goebel did not attach so much importance as many 

 other writers to phylogenetic considerations. He said that 

 the causes of metamorphosis are mainly internal and 

 belonging to the capacity of the individual plant, making 

 his idea of the process thus mainly an ontogenetic one, 

 though he held that the transformations actually seen in 

 organs are conditioned by a change of function. His 

 leaning to the side of the physiologists was clear. He 

 said, ' Metamorphosis is an actual objective fact ; the 

 rudiment which is normally destined to develop into a 

 definite organ may change its ordinary proportions during 

 development and thus give rise to another organ, and this 

 change of form is constantly associated with an alteration 

 of function. ... It is true that division of labour does 

 not necessarily involve metamorphosis, but it is a con- 

 dition of its manifestation. Hence not morphology, but 

 physiological requirement is the main factor, ideologically 

 speaking, in effecting structural differentiation.' 



GREEN p 



