120 



THE FLO]VEn 



IG 



A pollen grain of the 

 Pine, provided with 

 two air-tilled \'esi- 

 cles to give Imoyaney 

 in the air. 



234. Agencies and adaptations for intercrossing. — Tlie 



tiyents serving to transport poileii from llower to flower 

 lire wind, \\'att'r, anil small animals ( ina.inly insects). 



235. Pollination by wind. — Among the adaptations 

 displayed hy wind-pollinated flowers are to be mentioned 

 the chtiracter and quantity of the pollen produced. Tims 



the pollen grain of tlie 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 Conifer;e, are familiar. 

 Their pollen fills the air of a forest 

 during anthesis ; and the ' showers 

 of sulphur,' popularly so-called, the yellow po\vder which 

 after a transient shower accumulates as 

 a scum on the surface of water several 

 or many miles from the nearest source, 

 testifies to these particulars."^ All cat- 

 kin-hearing trees — except Willows — 

 an<l most gi'asses and sedges are "wind- 

 poUiiiated. Their flowers are mostly 

 dull-cohired, odorless, and 

 destitute of honey. The ^. 

 stigmas are relatively 

 prominent and apt to be 

 plumose (Fig. 1G6). The 

 anthers are often poised 

 on the tip of the filament 

 (Fig. ](i7), so that they 

 are shaken by tlie wind. 

 As tliey turn readily in all directions 

 they are said to be ciTXiitile. 



236. The pollen of aquatic plants is 

 sometimes carried from one flower to 



> Graj', "Structural Botany," p. 217 



ii^BiW* 



1117. A ^-ersalih 

 aiiflier. 



KB. Plumelikc stig- 

 mas of a grass. 



