CO-RELATION. 487 
There are certain co-relations which do not appear 
to have hitherto attracted the attention they merit ; 
such, for instance, is that which exists between the 
particular period at which an organ is developed 
and its position and form. In normal morphology 
this has, to some extent, been worked out, as in 
the case of definite and indefinite, centrifugal and 
centripetal inflorescences, and in the definite or in- 
definite formation of shoots, &c. 
Other instances may be cited in the frequent co- 
existence of regular flowers and definite inflorescence, 
the terminal position of many peloriated flowers, the 
relationship between indefinite inflorescence and pro- 
longation of the axis, &c. 
Again, the simultaneous evolution of the parts of the 
flower and their consequent verticillate arrangement, are 
often associated with the production of different forms 
from those characteristic of organs developed in succes- 
sion, and, in consequence, arranged spirally. In the case 
of simultaneous development we meet with a repe- 
tition of whorls, as in what are termed hose-in-hose 
flowers (flores duplicati, triplicati, &c.), and also with 
cases of peloria. In instances where the organs are 
formed successively in spiral order, we meet with such 
changes as median prolification, petalody, and phyllody. 
All these are alterations which we might anticipate from 
the activity of the growing point being checked at a 
certain stage in the one case, while it is continuous in 
the other. This relationship between the definite and 
indefinite modes of growth and the form of the several 
organs of the flower, is more constant in reality than 
it may appear to be from a perusal of the lists of 
genera in the foregoing pages, in which it was not 
possible to show sufficiently well the comparative 
frequency of any given changes in individual plants. 
Had it been possible to give statistics setting forth 
the frequency of certain deviations in plants or groups 
having a particular organisation, as compared with the 
rarity of their occurrence in other plants of a different 
