3 



cernecl A mountainous country is much more in need of forests than a low lying 

 country, on account of their beneficial action as regards landslips, avalanches, the 

 carrying away of debris, the silting up of rivers and lowlands, sudden floods, and 

 the sustained feeding of springs. As regards the protection against strong winds 

 and shelter to cattle and useful birds, forests act beneficially in any country." 



Whatever may be the ultimate policy of the country on the question of Govern- 

 ment forests, — a subject which involves the financial considerations of a large an- 

 nual expenditure, — private land-owners will always care to plant a few trees for the 

 sake of ornament ; some too will find the question of fuel an important one, others 

 that it is cheaper to grow their own lumber, others again may consider that it is 

 wiser to improve the quality of the soil of portions of their estates by growing 

 trees, than to leave it to gradual deterioration. 



Trees growing in woods require different principles of treatment from those 

 grown only for ornament or for their fruit. The treatment of woods on a ra- 

 tional basis constitutes the art of Sylviculture ; whilst the cultivation and care of 

 individual trees in a garden, or scattered in clumps over an estate, forms the 

 minor art of Arboriculture. 



FOOD OF TREES. 



Certain physical and chemical conditions are necessary for the well-being of 

 plants, and as the strength of a chain is measured by that of its weakest link, so 

 the development of a plant is governed by that factor which is at its lowest point. 



The action of warmth and of light are essential factors of a physical nature in the 

 growth of trees, and those of a chemical nature are carbonic acid, oxygen, and the 

 water which dissolves the mineral plant food in the soil. 



The effect of temperature may clearly be seen in Jamaica on ascending from 

 sea-level to various heights. Cashaw, mahogany, lignum-vitge grow at the lowest 

 elevations, cedar at mid-elevations, and Blue Mountain yacca at the highest al- 

 titudes. An extreme fall of temperature in Florida killed thousands of orange 

 trees. 



Light is necessary for the splitting up in the substance of the leaves of the 

 carbonic acid of the air, taken in through the breathing-pores, —and in fact it is 

 necessary for the whole nutrition. The intensity of light that is essential varies 

 not only for different species, but also for the same species under varying condi- 

 tions of soil and situation. Look at a tree growing in poor soil, it has smaller 

 leaves and a less dense crown of foliage than another growing in the rich soil 

 at the bottom of a valley. Trees growing in shade have leaves adapted to the 

 small amount of light they receive, and in thinning woods care must be taken 

 that such trees do not too suddenly receive more stimulus in the way of li^ht 

 than the leaves are at first cap ible of answering to, and thus disease be induced. 



Carbonic Acid is taken into the leaves from the air, and decomposed under the 

 action of light, forming carbon compounds which are used up in the growth of 

 the plant, 



Oxygen is always plentiful enough in the air for the purpose of respiratiou by 

 the leaves, but the roots of plants also require oxygen in the soil. Soil itself 

 cannot be fertile unless it is well aerated, and is frequently improved merely 

 through being kept open and porous by the roots of trees. 



Nitrogen is essential to the formation of the albuminoid substances of plants. 

 This substance is derived from the ammonia and other nitrogenous compounds 

 produced by the decomposition of decaying vegetable matter which compounds may 

 also be carried into the soil from the atmosphere by rain, or it may be derived 

 direct from the air by certain plants. The importance ot forests in improving the 

 soil is due not only to the aeration of large masses of the soil by the roots but 

 chiefly to the supply of humus or leaf-mould yielding nitrates to the soil. 



Water is necessary not only as a direct food, but as dissolving the food contained 

 in the soil. What is not required in the formation of the tissue of plants is 

 transpired or evaporated by the foliage into the atmosphere. The amount ne- 

 cessary varies according to the species, and for one and the same species according 

 to the nature of the soil and climate. The finer the particles of the soil, and the 

 larger the amount of humus the greater is the capacity for retaining moisture. 



Other important soil- nutrients, are lime, potash and phosphoric acid. 



SOIL IN RELATION TO WOODLAND GROWTH. 



Soil is due to the decomposition by various agencies of the rocks forming the 

 crust of the earth. A distinction is made between the soil or surface-soil and the 



