242 PHTLLODY 



place of other organs, is frequently looked on as due 

 to retrograde metamorphosis, or to an arrest of develop- 

 ment. But this is not strictly correct ; for instance, 

 suppose a petal, which is very generally merely the 

 sheath of a leaf, with the addition of colouring matter, 

 to be replaced by a perfect leaf, one in which all three 

 constituent parts, sheath, stalk, and blade, are 

 present, it surely can hardly be said that there has 

 been any retrogression or arrest of development in the 

 formation of a complete in place of an incomplete 

 organ. The term retrograde here is used in a purely 

 theoretical sense, and cannot be held to imply any 

 actual degradation. Morphologically, as has been 

 stated, the case is one of advance rather than the 

 reverse, and hence the assignment of instances of this 

 nature to a perversion of development, rather than to 

 a diminution or to an exaltation of that process, seems 

 most consistent with truth. The affected organs have 

 really undergone no actual change, simply the direction 

 of the organising force has been altered at a very early 

 state, so that the usual differentiation of parts has not 

 taken place. 



Phyllody of the bracts. As bracts are very generally 

 imperfect organs, so their replacement by perfect leaves 



Fro. 126. 'Rose plantain/ rhningo m^dia rir., spike contracted; 

 bracts leafy. 



