io6 



MORPHOLOGY 



petals, gamopetalous, hypogynous ; one whorl of an- 

 droecium with five stamens, free and epipetalous; and 

 one whorl of gynoecium with two carpels, syncarpbus, 

 ^ superior. The formula i Ps + s, Aa + gj, 



G;3) represents the structure of the 

 flower of rajani-gandha, namely, the 

 flower has a perianth of two whorls 

 of three leaves each, gamophyllous, 

 superior; androecium of two whorls 

 of three stamens each, free, superior; 

 and one whorl of gynoecium of three 

 carpels, syncarpous, inferior. Com-- 

 pare this formula with the floral diagram (fig. igo). 



Fig. loo. —Floral Dia- 

 gram of Liliaceae 



CHAPTER XV 



POLLINATION 



The first step towards reproduction is pollination, 

 which is the process of bringing the pollen-grains in 

 contact with the stigma in Angiospermia, and with 

 the ovules in Gymnospermia. When the pollen-grain 

 of a flower reaches the stigma or ovule of the same 

 flower, the process is known as self-pollination 

 or AUTOGAMY. Oh the other hand, when the pollen- 

 grain of a flower reaches the stigma or ovule of an- 

 other flower of the same species, whether on the same 

 plant or on a different plant, the process is known as 



CROSS-POLLINATION Or ALLOGAMY. 



An examination of the structure of flowers reveals 

 the fact that flowers may be arranged into several 

 groups according to the nature of their pollination. 



First, UNISEXUAL FLOWERS. Th'esc must be cross- 



