OF THE 



UNIVERSITY 



120 THE FLOWER 



165. A pollen 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 Coniferse, are familiar. 

 Their pollen fills the air of a forest 

 during anthesis ; arid 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 

 or many miles from the nearest source, 

 testifies to these particulars." 1 All cat- 

 kin-bearing trees except Willows 

 and most grasses and sedges are wiiid- 

 pollinated. Their 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 

 (Fig. 167), so that they 

 are shaken by the wind. 

 As they turn readily in all directions 

 they are said to be versatile. 



236. The pollen of aquatic plants is 1G6 pi ume iike stig- 

 sometimes carried from one flower to mas of a s rass - 



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



167. A versatile 

 anther. 



