

BOTANY OF THE LIVING PLANT 



modification of position of the stamens, which suggests that it may have 

 originated in different ways. It is represented also in the Gamopetalous 

 1 )icotyledons : these are divided into Tetracyclicae which have only one 

 whorl of stamens, and Pentacyclicae which have two ; making in all five 

 cycles of floral parts. The Pentacyclic type is prevalent also in the 

 Monocotyledons, as shown by the Liliaceous type of flower, with its many 

 derivatives. The biological meaning of such facts is to be found in 

 the larger supply of pollen thus provided to meet the risks of failure in 

 pollination. 



5T . 



Fig. 192. 



Flower of Scrophularia nodosa, which is pentamerous. The five stamens are 

 represented, but the posterior stamen (sf) has no anther : it is merely a vestigial 

 staminode which marks the place of a normal stamen. 



In " doubled " flowers similar features of pleiomery are seen. " Doubling " 

 often consists merely in a petaloid development of stamens ; and it most 

 commonly occurs in flowers with an indefinite number of stamens. But it 

 often involves also an actual increase in number of the petaloid parts, effected 

 by methods of fission, as well as of interpolation of extra whorls, or of extra 

 individual parts. 



(v) By Meiomery is meant that the number of parts of one category 

 stands below the fundamental number for the whole flower. It is 

 most often seen in the gynoecium ; but it appears also in the androe- 

 cium, especially in flowers where the mechanism is highly specialised. 

 It occurs less frequently in the outer floral parts. In the gynoecium 



