DISTRIBUTION OF SPORES AND SEEDS. 357 



withstand dryness. Most spores float in the air for some time 

 like dust particles, and the slightest current is adequate to 

 lift many and carry them along. Spores of most non-aquatic 



Fig. 402. — 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. The ones on the right 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 Kerner. 



fungi, mosses, and fernworts are distributed by air currents. 

 The microspores of some seed plants, especially the common 

 forest trees, are carried in this way. 



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

 plants, particularly, which have adapted themselves to the 

 distribution of spores by this means. The development of 

 the male plants in this group must be completed in the 

 neighborhood of the female plants, for the reason explained 

 in % 386. The microspores must, therefore, be carried to 

 the ovules of gymnosperms or to the stigmas of angiosperms 



