274 OUTLINES OF PLANT LIFE. 



to lift many and cany them along. Spores of most non- 

 aquatic fungi, mosses, and fernworts are distributed by air 

 currents. The pollen of some seed-plants, especially the 

 common forest trees, is carried in this way. 



Fig. 237. — Pollination of eel-grass {Vallisneria spiralis). The large flower is a pis- 

 tillate one, with stigmas fringed on under side. About it are floating staminate flow- 

 ers in various stages of development, having broken from submersed stems which 

 bore them. Tlie ones on the rignt and left have the boat-shaped perianth lobes turned 

 back, stamens mature, and pollen exposed ; one has floated so that the pollen is 

 brought into contact with the stigma of the pistillate flower. Magnified 10 diam. — 

 After Kemer. 



387. 4. By animals, especially insects. — It is the seed- 

 plants, particularly, which have adapted themselves to the 

 distribution of spores by this means. The pollen must be 

 carried to the ovules of gymnosperms or to the stigmas of 

 angiosperms and lodged there. It has been clearly shown 

 not only that adaptations for securing this result have been 

 developed, but also that there have arisen various ingenious 

 adaptations to secure cross-pollination and to prevent close- 

 pollination. (See ^ 295.) Some of these may be here 

 enumerated. 



