

CHAPTER I. 



ACCOUNT OF THE MATERIALS FROM WHICH PLANTS ARE FORMED; 

 MA TERIALS EXISTING IN THE AIR. 



1. I HAVE stated, that for the growth of our cultivated 

 crops, the essential conditions are the air, the soil, and water. 

 I say our cultivated crops, for it is familiar to us that a very 

 hirge class of plants, the weeds which grow so luxuriantly in 

 the sea that washes our coasts, and which, in some parts 

 of the world, navigators tell us, cover many miles of the 

 ocean, are wholly immersed in water, and derive no support 

 from the soil. But, though the sea-weed can extract from 

 the water all the materials required for its nourishment, 1 

 need scarcely say that the plants which we cultivate for food 

 require a soil, as well as water and air, for then* develop- 

 ment. Such, therefore, being the sources from which the 

 nutritive materials are derived that enable the seed to throw 

 out its stalk and root, and to produce substances adapted for 

 our use, it must be most interesting, and not without impor- 

 tant practical advantages for the fanner, to understand some- 

 tiiing of the part which the air, the water, and the soil, 

 severally peribnn in the nourishment of his crops. Fortu- 

 nately, the advance of organic chemistry within these few 

 years enables us satisfactorily to investigate many things 

 connected with this subject, which, formerly, it would have 

 been impossible to explain. 



2. It will be evident that, before entering upon this 

 inquiry, it is necessary that you should acquire a knowledge 

 of the simple bodies or elements of which air, water, and the 

 soil are composed, and of their properties; as, without be- 

 coming familiar with the materials upon which you have to 

 act, you cannot expect that you should successfully employ 

 them in regulating the development of vegetation. It will 

 require no great exertion of mind to obtain this knowledge, 

 and its possession will greatly facilitate your comprehension 

 of those beautiful processes by which the life of plants and 

 animals, and the harmony of creation, are maintained. 



B 



