INTRODUCTION. XXXI 



normally in Limnanthes and Crassula, and, indeed, 

 in a large proportion of all flowers in an early stage 

 of development. To a standard type, such as just 

 mentioned, all the varied forms that are met with, 

 either in normal or abnormal morphology, may be 

 referred by bearing in mind the different modifications 

 and adaptations that the organs have to undergo in 

 the course of their development. Some parts after a 

 time may cease to grow, others may grow in an 

 inordinate degree, and so on ; and thus, great as may 

 be the ultimate divergences from the assumed standard, 

 they may all readily be explained by the operation, 

 simply or conjointly, of some of the four principal 

 causes of malformation before alluded to. The fact 

 that so many and such varied changes can thus readily 

 be explained is not only a matter of convenience, but 

 may be taken as evidence that the standard of reference 

 is not wholly arbitrary and artificial, but that it is a 

 close approximation to the truth. 



It has already been said that an arrangement Hke 

 that here considered as typical is natural to some 

 flowers in their adult state, and to a vast number 

 in their immature condition. It would be no extrava- 

 gant hypothesis to surmise that this was the primitive 

 structure of the flower in the higher plants. Varia- 

 tions from it may have arisen in course of time, owing 

 to the action of an inherent tendency to vary, or from 

 external circumstances and varied requirements which 

 may have induced corresponding adaptations, and which 

 may have been transmitted in accordance with the 

 principle of hereditary transmission. This hypothesis 

 necessarily imphes a prior simplicity of organisation, 

 of which, indeed, there is sufficient proof; many cases 



