THE INFLUENCE OF WATER ON VEGETATION. 



ly opposed to each other. This partly arises from the accommodating jiature of plants, 

 and the infinite modifications of the various agents hy which they are influenced, render- 

 ing it extremely improbable for anj^ single observation to be of universal application. A 

 further cause of this diversity of opinion maybe found in the lucubrations of those who may 

 be termed speculators in vegetable physiology — " who are apt to draw general conclusions, 

 and raise axioms from every particular they meet with ;" and seldom hesitate in promulgat- 

 ing their ideas, and investing their theories, however crude they may be, Avith all the 

 " pomp and circumstance" of authenticated experiment. 



The importance of water to plants, and its influence upon them, may be readily con- 

 ceived, when it is known to form upwards of one-half of all green vegetable matter, and 

 serves as the means of conveyance for all the nutritive elements required for their food. 

 Mineral ingredients must be in a state of solution, or so minutely divided as to be carried 

 along with water, before they gain admission into the roots of plants. It is also supposed 

 that gaseous elements cannot be absorbed by roots in their ajriform state, and are availa- 

 able only when in solution with water. 



Seeing that water is not only a most important agent in vegetation, but is one more under 

 subjection than any other, it is evident that by its skilful application we can, to a great ex- 

 tent, regulate and control the groAvth of plants. It is true, that light, heat and air, are 

 also essential agents, and their co-operation indispensable, but over the first of these we 

 have no control, and the latter are under subjection only in artificial atmospheres; but 

 even in out-of-door culture, in fields and gardens, it is possible by draining and deep culti- 

 vation, to modify the injurious effects resulting either from excess or deficiency of water. 

 Our control over this agent enables us to meet extremes in the others. By its withdrawal 

 at certain seasons, and freer application of it in others, we can induce different develop- 

 ments, and hasten or retard their termination at will. 



Our possession of this controling influence is practically of most importance in the cul- 

 tivation of exotics, and the production of fruits and flowers out of their natural seasons. 

 Success in forcing depends chiefly upon the previous preparation of the plants for that pur- 

 pose; an early and thorough ripening of the previous growth, with a proper period of rest, 

 are absolutely indispensable. This is effected by a gradual withdrawal of water. If we 

 lessen the supply of water to a growing plant, we of course cut off" the means whereby 

 nourishment is conveyed into its system. Alkalies and other inorganic substances held in 

 solution, are constantly convej^ed to the plant with the water absorbed by the roots, these 

 co-operate with the carbonic acid absorbed by the leaves in forming new constituents of the 

 plant. When water is withheld fi'om the roots this supply of mineral ingredients is cut 

 off"; these are then taken from the plant itself, principally from the juices of the leaves, 

 which soon begin to change color, and ultimately fall off"; while the substances by which 

 they were upheld are incorporated into woody fibre, or other matters necessary for the 

 structure of the plant. (Liebig.) And " rest in plants is effected in one or two waj's; either 

 by a very considerable lowering of temperature, or by a degree of dryness under which 

 vegetation cannot be sustained." (Lindley.) 



The inflorescence of plants is increased by a diminished supply of water Avhile the buds 

 are being formed; anything, indeed, that tends to check luxuriance — so long ss the plant 

 is in a healthy state, is favorable for the production of flowers. The rudiments of flower 

 buds bear a striking resemblance to leaf buds, they are formed of the same elements, and 

 may be mutually transformed into each other according to circumstances. ]\Iost gardeners 

 aware that an over supply of nourishment has a tendency to promote the development 

 instead of flower buds. Hence we find fruit trees planted in rich, stimulating soil 



No. II. 37 



