CHAPTER IV. 



PRINCIPLES OF GARDENING. 



" Ouare agite o. proprios generatim discite cultus, 

 Agricolas, fructusque feros mollite colendo ; 

 Neu segnes jaceant terrae." VIRGIL. 



THERE are certain physiological principles which must be kept in 

 mind by every gardener who desires to practise his art with 

 success. The plants which he cultivates are built up of cells, and each 

 plant is developed from a pre-existing cell or series of cells ; and hence 

 it is not within the range of human power to make a plant from any 

 primary elements, and even did we know perfectly the elementary 

 substances of which a plant is composed, no person could put them 

 together to make a plant. 



Some persons do indeed believe that, under favourable circum- 

 stances, a plant may be formed of inorganic matter, but their belief 

 is founded upon unexplained phenomena connected with the lower class 

 of plants, and their speculations rather partake of fancy than of fact. 



Throughout the whole range of cultivated plants there is a unity of 

 design, a unity of obedience to certain fixed laws, which has led some 

 minds to think that there is but one plant, which time and circum- 

 stances have modified into many varieties now separated as species. 



Gardeners know as a fact that every plant is subject to variation 

 within certain limits ; hence the origin of florist's flowers. There are 

 more than a thousand varieties of camellias, a thousand varieties of 



