INTRODUCTION, XXX] 
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 
ordinate 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 like 
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 implies a prior simplicity of organisation, 
of which, indeed, there is sufficient proof; many cases 
