476 GENERAL MORrnOLOGY. 



growth up to a certain point and is then stopped, and 

 thus changes are brought about in the part affected 

 of a different nature from those dependent on non- 

 development or suppression. 



Some malformations are congenital, therefore, while 

 others are acquired in the former instance the dis- 

 turbance is coeval in origin, and contemporaneous in 

 its growth and development, with those of the affected 

 part ; in the latter case the organ may have attained 

 its ordinary degree of perfection, or at least may have 

 advanced some way towards it, before any deviation 

 shows itself. True chorisis or fission, for instance, is 

 usually a congenital affection, arising at a very early 

 period of development, while enation takes place from 

 structures which are all but complete as to their 

 organisation, even though they may not have attained 

 their full dimensions. The date of appearance is also 

 of consequence in determining the true nature of some 

 changes ; it does not always follow, for instance, that 

 because one organ occupies the position of another, 

 it is of the same nature as the one whose place it 

 fills. The presence of anthers on petals or on such 

 organs as the corona of Narcissus does not necessarily 

 constitute those parts actual stamens, but rather 

 staminodes. The true stamens are either wanting, or 

 if present, they are in advance of their imitators as 

 regards their development. 



General morphology of the leaf and axis. Homology. Since 

 the time when Goethe's generalisations were adopted 

 by A. P. De CandoUe, special attention has been given 

 to the form and mode of development of the leaf- 

 organ ; for as it was well said by Wolff, if once the 

 course of evolution and the structure of the leaf were 



