Flowers. 



177 



the younger flowers to the stigmas of the older, or vice versa 

 in case of proterogyny. In dimorphic flowers the pollen 

 from short anthers would quite certainly be deposited by 

 insects on the stigmas of the short pistils, as in going 

 from B to A, Fig. 91. 



Adaptations for cross fertilization are perhaps best seen 

 in the various adjustments of flowers to the agents which 

 are to transport the 

 pollen and deposit it 

 on the stigma. These 

 agents, as has been 

 stated, are wind, in- 

 sects and other ani- 

 mals, and water. 



127. Adaptation to 

 Wind. Those flow- 

 ers which depend 

 upon the wind for 

 transporting the pol- 

 len are characterized 

 by protruding stamens and a relatively large expanse of 

 stigmatic surface ; this is well shown by Indian corn, 

 whose staminate flowers surmount the plant and send forth 

 numerous pendent stamens which offer their pollen to the 

 wind. The long silken styles which protrude beyond the 

 husks of the pistillate inflorescence, or ear, present a 

 large surface for arresting the pollen as it is being carried 

 about by winds. 



The pines, poplars, and willows illustrate the same 

 thing in somewhat different ways. The pollen of the pine 

 is borne in great abundance in the staminate catkins (see 

 Fig. 92), and each grain is provided with two balloon-like 

 expansions containing air, which contribute to its lightness 



FIG. 92. 



Staminate catkin of the Pine. 



