THE FLOWER 13 



development is persistent among flowers, the first set showing 

 it being the carpels, resulting in syncarpy. The zonal develop- 

 ment of the corolla, however, or sympetaly, accords with so 

 many other characters indicating natural relationships that it 

 has been used to designate and even to define the great group 

 Sympetalae. This is probably pressing a single character too 

 far, for there is evidence that the result has been to do violence 

 to certain natural relationships, and to make certain unnatural 

 groupings. This tendency to zonal development is found in 

 every floral set, and those flowers that show it are certainly 

 to be regarded as of higher rank than those that do not. 



Among the more primitive flowers each cycle arises sep- 

 arately from the growing point, its members remaining separate 

 or the whole meristematic zone entering more or less completely 

 into the outgrowth. The insertion of each cycle is definitelv 

 below that of the next inner cycle, resulting in an hypogynous 

 flower (Fig. 1, A). That hypogyny is a primitive condition of 

 the flower is a statement that does not seem to need discussion. 

 The tendency to zonal development, however, is carried farther 

 when a whole region arising en masse produces two or more 

 cycles of floral members. In the simplest cases two cycles are 

 thus produced, as is illustrated by the strong tendency of the 

 petaliferous and staminiferous cycles to have a common origin 

 in sympetalous flowers, resulting in the appearance of " stamens 

 inserted on the tube of the corolla." The same tendency is 

 shown among orchids, in which the whole region for the devel- 

 opment of stamens and carpels arises in a single body, forming 

 the characteristic gynostemium or " column." While these may 

 be regarded as special tendencies of certain groups, rather than 

 of flowers in general, there are other instances that seem to 

 belong to the general evolution of the flower. In certain cases 

 the region of the growing point belonging to the carpels ceases 

 to develop, while the rest of the growing point continues to 

 develop en masse, forming a cup or urn-like outgrowth, from 

 the rim of which the three outer sets develop separately, form- 

 ing the perigynous flower (Fig. 1, B). In this case the carpels 

 arise from what seems to be a depression in the center of the 

 torus, but which, of course, is the region of checked growth. 

 Perigyny is chiefly displayed among families of the Archi- 

 chlamvdeae. 



