REPRODUCTION 



185 



This consists typically of those structures intimately concerned 

 with the development of tlu^ sexual cells, together with others 

 which contribute indirectly to the success of the process of repro- 

 duction (Figs. 97 and 98). 



Stamens and Pistils. — The essential organs of the flower are the 

 stamens and piMiLs. P^ach stamen bears an anther or pollen sac. 



|-Anther 

 Filament 



-S+igma 

 .Style 



Petal 



Stamen 



i 



Pi&ti 



-Chambers 

 of Ovary 



■ Ovule 



Cross Sectio' 

 of Ovary 



Sepal 



Fig. 97. — The structure of the flower of a dicotyledonous .secd-phuit (diagram- 

 matic). .4, face view of the flower, showing its calyx of five sepals, its corolla 

 of five petals, its ten stamens, and its pistil. B, longitudinal section, showing the 

 relations between the parts. 1, receptacle. 2, calyx. 3, corolla. 4, stamen. 

 5, pistil, with ovary cut lengthwise. 



and within this sac are produced a great number of minute, 

 single-celled 'pollen grains (Fig. 99), from the contents of each 

 of which two male gametes ultimately develop. The anther is 

 commonly supported by a stalk or filament. The pistil consists 

 of a closed chamber, the ovanj, at the top of which is the stigma, 

 a structure adapted to catch and hold the pollen grains. The 

 stigma is often supported by a stalk or sti/le. In the ovary are 

 borne the ovules or potential seeds, within each of which is a 

 female gamete or egg. The fertilization of an egg by a male gamete 

 starts the series of processes which result in the (l(>v(>l()pin(Mit of 

 the ovule into a seed. 



