328 HORTICULTURE, FORESTRY, FLORICULTURE 



GENERAL PRINCIPLES OP FORESTRY FOR FARMERS. 



This country varies so greatly in soil, climate, and flora that it 

 is only possible, within the limits assigned for the present discus- 

 sion, to outline general principles everywhere applicable. Wher- 

 ever suggestions nave approximated the laying down of rules of 

 practice, the writer had mainly in mind the conditions prevalent in 

 our northeastern States. 



The succeeding chapters should be read connectedly. The first 

 treats of the behavior of a forest plant ; the second, of the principles 

 which should guide the planter in setting a crop ; the third, of the 

 manner in which a natural forest crop should be produced; and 

 the fourth chapter points out how the crop should be managed 

 afterwards in order to secure the best results in quantity and quality 

 of material. 



How Trees Grow. Trees, like most other plants, originate from 

 seed, build up a body of cell tissues, form foliage, flower, and fruit, 

 and take up food material from the soil and air, which they convert 

 into cellulose and other compounds, from which all their parts are 

 formed. They rely, like other plants, upon moisture, heat, and 

 light as the means of performing the functions of growth. Yet 

 there are some peculiarities in their behavior, their life and growth, 

 which require special attention on the part of a tree grower or forest 

 planter, and these we shall briefly discuss. 



Trees derive their food and solid substance in part from the air 

 and in part from the soil. The solid part of their bodies is made up 

 of cellulose, which consists largely of carbon (44 per cent of , its 

 weight), with hydrogen and oxygen added in almost the same pro- 

 portions as in water. The carbon is derived from the carbonic acid 

 of the air, which enters into the leaves and, under the influence of 

 light, air, and water, is there decomposed; the oxygen is exhaled; 

 the carbon is retained and combined with elements derived from 

 the water, forming compounds, such as starch, sugar, etc., which 

 are used as food materials, passing down the tree through its outer 

 layers to the very tips of the roots, making new wood all along the 

 branches, trunk, and roots. 



This process of food preparation, called "assimilation," can be 

 carried on only in the green parts, and in these only when exposed 

 to light and air; hence foliage, air, and light at the top are essen- 

 tial prerequisites for tree growth, and hence, other conditions being 

 favorable, the more foliage and the better developed it is, and the 

 more light this foliage has at its disposal for its work, the more vig- 

 orously will the tree grow. In general, therefore, pruning, since it 

 reduces the amount of foliage, reduces also, for the time, the amount 

 of wood formed ; and just so shading, reducing the activity of foliage, 

 reduces the growth of wood. 



Soil Conditions. From the soil trees take mainly water, which 

 enters through the roots and is carried through the younger part 

 of the tree to the leaves, to be used in part on its passage for food 

 and wood formation and in part to be given up to tV,e air by 

 transpiration. 



