152 ACTION OF THE SOIL ON PLANTS. 



means of her elementary agents, air and water. If the 

 rock be of a calcareous nature, the lime is gradually dis- 

 solved, a decomposition begins to be effected ; and hence 

 the origin of a soil. If the rock be silicious the opera- 

 tion is more difficult ; but Nature, unrestricted by time, 

 finally accomplishes her object. On this shadow of a 

 soil, a vegetation, almost imperceptible from its minute- 

 ness, begins to exist : the invisible seeds of lichens, which 

 are ever floating in the air, there find an asylum. Minute 

 as these seeds are, they are furnished with admirable 

 means to attach themselves to hard bodies. 



Caroline. What a careful provision Nature has made 

 for the most insignificant of her vegetable kingdom ! 



Mrs. B. These seeds, once attached to the rock, find 

 sufficient nourishment in the moisture they have absorb- 

 ed from the atmosphere during their aerial flight to enable 

 them to germinate, but not sufficient to bring them to 

 perfection, and enable them to produce seeds to contin- 

 ue their species ; but when they perish, a new race rises, 

 phoenix like, from their remains. 



Emily. This is indeed a new mode of raising plants ! 



Mrs. B. It is these remains, mixed up with some of 

 the crumbled particles of the rock, which constitute the 

 first bed of earthy soil, in which the seeds of more robust 

 lichens arid mosses sow themselves, and find nourish- 

 ment ; thus a variety of plants, annually increasing in 

 strength and vigor, rise up in succession, till the dry rock 

 becomes covered with verdure, and ultimately clothed 

 with trees. You see, therefore, Caroline, that you have 

 no more reason to despise the humble plants in whose 

 remains a soil originates, than to underrate the germ of 

 a shoot which may produce a stately oak. 



There is another process which nature frequently em- 

 ploys to clothe a barren rock : wherever there are fissures 

 the rain insinuates itself, and by freezing in winter of- 

 ten splits the rock, or at least widens the crevices ; it is 

 in these humid recesses, where the water has crumbled the 



838. How does nature begin in forming soil upon a rock 1 ? 839. 

 What is the first vegetable appearance 1 ? 840. From whence do the 

 seeds of lichens floating in the air obtain sufficient moisture for germina- 

 tionl 841. -What is the successive process by which soil is formed on 

 rocks from the growth of vegetables 1 842, What is another process 

 by whic,h nature clothes a barren rock 1 ? 



