BOOK II. 
DEVIATIONS FROM THE ORDINARY FORM OF ORGANS. 
Ivy a morphological point of view the form of the 
various parts or organs of plants and the changes to 
which they are subjected during their development 
are only second in importance to the diversities of 
arrangement and, indeed, in some cases, do not in any 
degree hold a second place. 
Taken together, the arrangement, form, and number 
of the several parts of the flower, make up what has 
been termed the symmetry of the flower.’ Referring 
to the assumed standard of comparison, see p. 4, it 
will be seen that in the typically regular flower all the 
various organs are supposed to be regular in their 
dimensions and form. At one time it was even sup- 
posed that all flowers, no matter how irregular they 
1 The word symmetry has been used in very different senses by different 
botanists, sometimes as synonymous with “regularity,” at other times 
to express the assumed typical form of a flower. Payer understands it 
_ to be that arrangement of parts which permits of the whole flower being 
divided vertically into two symmetrical halves (bi-lateral symmetry). 
Others, again, have applied the term symmetry to the number of the 
parts of the flower, reserving the terms “regularity” or “irregularity” 
_ for the form. It is here used in a general sense to express the plan of the 
flower, and thus includes the arrangement, form, and number of its 
component elements. 
