DISSEMINATION OF SEEDS. 123 



"It is a law of nature that plants shall be diffused as 

 widely as possible wherever the circumstances are favor- 

 able for their growth and welfare." The agents employed 

 in the carrying out of this law with reference to plants 

 are more numerous than those employed in the distribu- 

 tion of any other class of objects. This is largely due 

 to their mode of propagation by seeds, to the length of 

 time that seeds retain vitality, to the great extremes 

 of heat and cold, of drought and moisture which they 

 can endure without injury to the germ. 



First among the natural modes of dissemination of the 

 seed, because the most common, may be mentioned that 

 produced by the action of the wind. 



DISSEMINATION OF ' SEEDS BY THE WIND. % 



The wind is one of the most efficient agents in the dis- 

 persion of seeds. The seeds formed by very many plants 

 are minute, almost microscopic in size, and, when the 

 seed-vessels which contained them burst, they float in the 

 air until they reach a suitable place in Avhich to germinate. 

 Here signs of life begin to manifest themselves, the seeds 

 burst their outer coverings, roots are formed, stems and 

 leaves expand, and under the influence of light, heat, air, 

 and moisture, plants flourish which, in their turn, develop 

 seeds and scatter them broadcast through the air. The 

 spores of lichens, mosses, and ferns are in this way scat- 

 tered by the wind and, being very numerous, wherever 

 the soil is adapted to the growth of such plants they 

 cover it with their peculiar verdure and in many cases fit 

 it for the growth of higher orders of plants. The seeds 

 of many flowering plants are small, but very abundant. 

 They are enclosed in peculiar capsules and, as these are 

 moved to and fro by the wind, the seeds are scattered 



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