240 



PRACTICAL COURSE IN BOTANY 



as it must now depend upon the conveyance of pollen to the 

 stigma by extraneous means. 



274. Adaptations to wind pollination. — A very large 

 number of plants, among which are included nearly all our 



principal forest trees, grains, 

 and grasses of every kind, 

 depend exclusively upon the 

 wind for the distribution of 

 their pollen. This being 

 the case, it is, of course, an 

 advantage to them to get 

 rid of all unnecessary ap- 

 pendages that might hinder 

 a free play of the wind 

 among their flowers, and so 

 they consist, as a rule, of 

 essential organs only (Figs. 

 34 1 , 342) . Such flowers are 

 often distinguished, how- 

 ever, especially among 

 grasses and low herbs, by 

 large, feathery stigmas that 

 are well adapted to catch and hold any stray pollen grains 

 which may be floating in the air. Place a stigma of oat or 

 other grass under the microscope and you will probably see 

 a number of pollen grains clinging to its branches. 



275. The disadvantages of wind pollination. — This is a 

 very clumsy and wasteful method, however, for so much 

 ]:>()llen is lost by the haphazard mode of distribution that the 

 plant is forced to spend its energies in producing a vast 

 amount more than is actually needed, and great masses of it 

 are frequently seen in spring floating like patches of suli)hur 

 on ponds and streams in the neighborhood of pine thickets. 

 Like those that are self-pollinated, wind-pollinated flowers 

 are generally very inconspicuous, devoid of odor, and of all 

 attractions of form or color^ because they have no need of 



Fig. 351. — Feathery stigmas of a grass 

 adapted to wind pollination. 



