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A TEXTBOOK OF BOTANY 



[Ch. VI, 5 



and staminate flowers, which become loosened and rise to the 

 surface ; here they float about until they touch a stigma of 

 the floating pistil, when fertilization is effected in the usual 

 way. Afterwards the pistil is drawn deep under water, and 

 held there during ripening by the spiral coiling of the stalk. 

 Such water-pollinated flowers are mostly so inconspicuous 

 as not to be popularly recognized as flowers at all. They 

 exhibit, indeed, no other floral characteristics than the 

 possession of the comparatively obscure, even though vastly 

 important, stamens and pistils, although some kinds possess 

 rudimentary petals and sepals as relics of their evolutionary 



history. Some water 

 plants, however, no- 

 tably the Water-lilies, 

 retain their showy 

 flowers pollinated by 

 insects. 



In the flowering land 

 plants the simplest 

 agency of pollination 

 is the wind. Wind- 

 pollination occurs in 

 most of our trees, e.g. 

 Elms, Birches, Oaks, Pines; in some shrubs, e.g. Alders; 

 and in a few herbs, — notably Grasses, including the 

 Corn. A typical case is the Hazel (Fig. 197), in which 

 the long dangling catkins are clusters of staminate flowers, 

 while the pistillate flowers are so few and inconspicuous as 

 to require special search even by the trained eye of the bot- 

 anist, and would hardly be recognizable at all were it not for 

 the relatively prominent feathery stigmas. When ripe, the 

 pollen, easily shaken from the catkins by a touch, is wafted 

 about on the lightest breezes, so that some of it comes into 

 contact with the stigmas, though of course an overwhelming 

 preponderance is wasted. This case illustrates the typical, 

 though not invariable, features of wind-pollinated flowers, 



Fig. 200. — Dichogamous flower of Scrophu- 

 laria nodosa; X 2. 



Left, a flower with ripe stigma but unripe 

 stamens, shown better in the section (middle 

 figure) ; right, a flower with ripe stamens 

 but withered stigma. (After Warming.) 



