364 



FOUNDATIONS OF BOTANY 



which are unripe, shut together, and tucked aside out of 

 reach. On flying to a flower in the later stage the pollen 

 just acquired will be lodged on the prominent stigmas and 

 thus produce the desired cross-pollination. 



--sag 



I II III IV 



FIG. 256. Provisions for Cross-Pollination in the High Mallow. 



I, essential organs as found in the bud ; II, same in the staminate stage, the 

 anthers discharging pollen, pistils immature ; III, intermediate stage, 

 slig, the united stigmas ; IV, pistillate stage, the stigmas separated, 

 stamens withered. 



Closely related flowers often differ in their plan of 

 pollination. The high mallow, a plant cultivated for its 

 purplish flowers, which has run wild to some extent, is 

 admirably adapted to secure cross-pollination, since when 

 its stamens are shedding pollen, as in 

 Fig. 256, II, the pistils are incapable of 

 receiving it, while when the pistils are 

 mature, as at IV, the stamens are quite 

 withered. In the common low mallow 

 of our dooryards and waysides insect 

 pollination may occur, but if it does not 



FIG. 257. Stamens *' 



and Pistils of Round- the curling stigmas finally come in con- 

 Leafed Maiiow. The il(ici ^fa ih& pro j e ctmg stamens and 



stignvas curled round 



among the stamens receive pollen from them, as is indicated 



to admit of self-pol- . T -,. ctrn 

 lination. "1 tig. 257. 



