382 WATERING. 



ancc ; but in groves of trees, and in plantations formed in Mr. Cree's 

 manner, there will always be spaces more or less liable to throw up 

 rampant weeds, which in merely useful plantations ought to be mowed and 

 left to decay on the spot, for the sake of the manure which they will afford 

 to the trees. In cultivated or smooth park scenery, all coarse weeds should 

 begot rid of, so as to present a smooth turf; but in rough forest park 

 scenery, all the plants which it produces should be allowed to grow as being 

 appropriate : of these, the large fern or brake (pteris aquilina) is peculiarly 

 characteristic. 



820. Weeding ponds, rivers, and artificial waters, in garden and park 

 scenery, is often very expensive by its being necessary to empty and clean 

 out the bottom and sides of the excavation. Much of this trouble and 

 expense might be rendered unnecessary in many cases by mowing over the 

 weeds in the bottom of the water, when they first make their appearance 

 there in early spring, and repeating the operation at short intervals till the 

 roots are destroyed from the want of elaborated sap sent down by the leaves. 

 (See more on this subject in par. 548.) It should be constantly borne in 

 mind, that all weeds and all plants whatever may be effectually destroyed by 

 depriving them of their leaves as fast as they are produced (113). 



XII. Watering. 



821. Water, whether as a source of nutriment or a medium of affecting 

 various other objects, is one of the most important agents of culture. A 

 certain degree of moisture in the soil is essential to the existence of plants ; 

 because no food can be absorbed by the roots that is not held in solution 

 by water, and because the decomposition of water, and its perspiration from 

 the leaves and bark are continually going forward. Plants require a certain 

 degree of moisture at their roots not only when in active growth, but when 

 in a state of comparative rest, because even then perspiration is going on 

 with those parts which are above the ground, and with the roots themselves 

 when plants are taken up for transplanting. In the season of growth the 

 demand for water is greatly increased, and it diminishes as the period of 

 growth advances, and the power of decomposition and evaporation ceases. If 

 water in excess is given at this period of the growth of a plant, its parts 

 become distended in consequence of the absorption by the spongioles still 

 going on, while the power of decomposition and perspiration by the leaves is 

 diminished ; it becomes sickly, its leaves assume a yellow colour, and if the 

 excess of water is not soon withdrawn from the soil, death ensues. By 

 pulverizing soils and increasing their depth, their capacity for holding water 

 is increased, while by underground draining it cannot be retained in excess. 

 By these means, and by the addition of immures acting mechanically 

 and keeping the soil open, a great facility is afforded to the extension of 

 the roots, and the vigour of the plants is increased in proportion, but at 

 the same time the power of the roots to exhaust the soil of water becomes 

 greatly increased. If under such circumstances a proportionate supply 

 of water is not afforded at the proper time, either by nature or art, 

 the growth of the plant will fall much short of what it might be ; of which 

 examples may be seen both in garden and field crops, by comparing the crops 

 of a moderately wet summer with those of a very dry one. It may be con- 

 cluded, therefore, that the full benefits of stirring the soil, draining and 

 manuring, cannot be obtained without a command of water. 



