120 



THE FLOWER 



165 



A polleu grain of the 

 Pine, provided with 

 two air-filled vesi- 

 cles to give buoyancy 

 in the air. 



234. Agencies and adaptations for intercrossing. — The 

 agents serving to transport pollen from flower to flower 

 are wind, water, and small animals (mainly insects). 



235. Pollination by wind. — Among the adaptations 

 displayed by wind-pollinated flowers are to be mentioned 

 the character and quantity of the pollen produced. Thus 



the pollen grain of the Pine con- 

 sists of three compartments, the 

 two lateral ones empty and serving 

 as wings (Fig. 165). "The im- 

 mense abundance of pollen, its 

 lightness, and its free and far diffu- 

 sion through the air in Pines, Firs, 

 and other Coniferte, are familiar. 

 Their pollen fills the air of a forest 

 during anthesis ; and the ' showers 

 of sulphur,' popularly so-called, the yellow powder which 

 after a transient shower accumulates as 

 a scum on the surface of water several i 



or many miles from the nearest source, 

 testifies to these particulars."^ All cat- 

 kin-bearing trees — except Willows — 

 and most grasses and sedges are wind- 

 pollinated. Th^ir flowers are mostly 

 dull-colored, odorless, and 

 destitute of honey. The 

 stigmas are relatively 

 prominent and apt to be 

 plumose (Fig. 166). The 

 anthers are often poised 

 on the tip of the filament 

 167. A versatile (Fig. 167), SO that they 

 are shaken by the wind. 

 As the}^ turn readily in all directions 

 they are said to be versatile. 



236. The pollen of aquatic plants is 

 sometimes carried from one flower to 



1 Gray, "Structural Botany," p. 217. 



^, 



*i^>;fs$s?»i 



166. Plumelike stig- 

 mas of a grass. 



