122 



PRINCIPLES OF PLANT-TERATOLOGY. 



Angiosperm has been evolved out of an elongated 

 shoot bearing well-developed foliage-leaves which were 

 in part fertile. This view was probably originally 

 founded on teratological data; sepals, petals, stamens, 

 and carpels were observed to frequently change into 

 foliage-leaves ; but partly, perhaps, on facts of onto- 

 geny, in which the rudiments of both floral and foliage- 

 leaves were seen to arise and develop in the same way. 

 But there is no value to be attached to this last fact. 

 Floral leaves must be supposed to arise congenitally 

 as such ; a stamen is a stamen and nothing else from 

 its birth onwards, and there is no evidence that in the 

 ontogeny it passes through any foliage-leaf stage. 

 Hence Goebel must be held to be in error in ascribing, 

 without adducing any evidence, foliage-leaf nature to 

 every rudiment of a floral leaf. The rudiment is, 

 admittedly, a plastic structure, and may, under certain 

 conditions of nourishment, etc., be capable of develop- 

 ing into a foliage-leaf. In fact every floral leaf may 

 be regarded as having the potentialities of every other 

 and of a foliage-leaf ; but that is a different thing from 

 assuming that foliage-leaf nature must still inhere in 

 every floral leaf in the earliest stage of its ontogeny, 

 for this implies a denial of its congenital value as a 

 floral leaf. 



We have in the last few years had strong grounds 

 for holding the view that both recent and Mesozoic 

 cycads have been derived by descent from the Pterido- 

 s perms of the Coal Period. The latter possessed 

 sporophylls of, for the most part, great complexity, 

 fern -like in organization, and in some cases, either in 

 whole or in part, foliaceous and assimilating, like the 

 sporophylls of modern ferns. It is probable that the 

 shoots bearing sporophylls of this nature are the actual 

 progenitors of the flowers or cones of the Mesozoic and 

 recent cycads. The sporophylls became very greatly 

 reduced in complexity of organization and in size. 

 The excessively simplified male and female sporophylls 

 (stamens and carpels) of a modern cycad, or the female 



