RELATION TO ENVIRONMENT 



515 



appear before the leaves unfold, so that pollen more readily reaches 

 the pistillate flowers. Where anemophilous flowers are hermaphro- 

 dite, they are almost always dichogamous, i.e. stamens and pistils 

 mature at different times, so that self-fertilization is impossible. 



Hydrophilous Flowers 



A few water-plants have special modifications for pollination. In 

 the submersed flowers of Naias, Zostera, Phyllospadix, etc., the 

 pollen-spores are more or less elon- 

 gated, sometimes threadlike, and 

 are thus more easily caught by the A 



stigma. In Vallisneria the stami- 

 nate flowers, which are enclosed in 

 a spathe-like envelope, break away 

 at maturity, and rise to the surface 

 of the water, where they open and 



FIG. 481. Vallisneria spiralis. A hydro- 

 philous plant. A, pistillate flower ready 

 for pollination. B, male inflorescence. C, 

 single open staminate flower, enlarged ; 

 the reflexed sepals serve as floats. 



FIG. 482. Carex sp. An anemophi- 

 lous plant; the staminate flowers, 

 6, are placed above the pistillate 

 ones, V . B, staminate flower, en- 

 larged. C, pistillate flower. 



float about until they come in contact with the expanded stigmas 

 of the pistillate flowers which lie at the surface when ready for 

 pollination. After the pollen is deposited upon the stigmas, the 

 female flower is drawn beneath the surface of the water by the coil- 

 ing of its stalk, and the fruit ripens under water. 



