EXERCISE 51 

 CAN POLLEN BE DISTRIBUTED BY WIND? 



Materials. Any of the following which may be in flower at the 

 proper season : cornstalks in tassel ; pine trees or cedar trees with 

 staminate cones ; maple, box elder, willow, poplar, or ash trees in 

 blossom ; timothy or other grasses in flower ; ragweeds. 



Directions for work. Select for study several species if pos- 

 sible. Examine the flowers to identify stamens and pistils. In 

 many species the stamens and pistils do not occur in the same 

 flower,, and often not on the same individual. What relation 

 does this have to the 'prevention of self-pollination ? 



Note the character of the pollen and its abundance. Is it 

 moist and sticky or dry and powdery? Is it of such character 

 as to be readily carried by the wind? Jar a flower-bearing 

 branch on which you have discovered ripe anthers. Does the 

 pollen fall from the flowers, and is it carried away by the wind ? 



Do the pistils appear to be well adapted to catch flying 

 pollen ? It is suggested that pistils which extend beyond the 

 calyx and corolla, if these are present, and pistils which have 

 long or feathery stigmas would be more likely to intercept 

 flying pollen than pistils of the usual sort. 



Is this method of pollination economical or wasteful of pollen ? 

 Is the pollen abundant or scanty in amount in the plants studied? 



Sum up your entire study in a brief statement of what it 

 has shown you about the possibilities of wind pollination. Com- 

 pare the wind-pollinated plants and tell what features you find 

 common to most of them. In what respects are their flowers 

 commonly different from those of the insect-pollinated plants ? 



References 



BERGEN and CALDWELL. Practical Botany, p. 120. 

 BERGEN and CALDWELL. Introduction to Botany, p. 143. 



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