NATURE OF PLANTS. 195 



that would produce leaves and twigs if left in the air, 

 will throw out roots if put in the earth. This is the 

 foundation of the art of obtaining ready grown trees 

 by cuttings and layers. In some instances, as in that 

 of the willow, it is of no consequence which end of the 

 cutting is set in the ground; and if both are set they 

 will often take root, and the buds and branches grow 

 up at the middle between them. The stem of an ivy also 

 will throw out roots as long as it is in the shelter of 

 a wall, although it should not be actually in contact 

 with it ; but as soon as it rises above the wall, and the 

 wind acts freely upon all sides of it, not another root 

 appears upon the bark. 



Thus plants, if properly studied, would of themselves 

 make the spring a busy time for the mind ; and as the 

 greater part both of our property and our enjoyment 

 comes from plants, they claim a very large portion of 

 our attention ; the more so, that we could not have 

 an animal without them, as these are all supported 

 directly by plants, or at second hand by other animals 

 that the plants support. Of the operations that take 

 place upon that curious confine, where the organic and 

 the inorganic departments of creation are blended with 

 each other, we are but imperfectly informed ; and of 

 the specific food of plants, we know not a great deal 

 more, but we have reason to conclude that organic 

 matter, either in the living state or in the dead, is that 

 which is most generally and readily assimilated both by 

 animals and by plants. The knowledge of the struc- 

 ture and functions of plants is one of which we must 

 know something, otherwise the rest of our knowledge 



