Analogy between Plants and Animals. 415 



resent injuries, either negative or positive, by slow growth, or by 

 becoming diseased. By their being fixed to the spot where they 

 grow, they necessarily depend for their food, heat, air, and light, 

 on the circumstances peculiar to that spot; and, hence, to increase 

 their growth beyond what it would be if left to nature, addi- 

 tional food must be brought to them, and the warmth, airiness, 

 and lightness of the situation increased. Hence, what is called 

 vegetable culture ; which consists in stirring the soil, adding ma- 

 nure to it, regulating the supply of water by draining or irriga- 

 tion, sheltering from the colder winds, and exposing to the direct 

 influence of the sun's rays. If we imagine anj' one of these 

 points attended to, and not the others, the plant will not thrive. 

 Stirring the soil, and mixing it with manure, will be of little use 

 if that soil be liable to be continually saturated with moisture, 

 either from its retentive nature, from springs from below, or from 

 continued rains from above; or if it be continually without, or 

 with very little, moisture, from its porous natui'e, the want of 

 moisture in the subsoil, and the want of rain and dews from the 

 atmosphere. Improving the soil without improving the climate 

 (that is, without communicating a proportionate degree of warmth 

 and light) will increase the bulk of the plant, but without pro- 

 portionately bringing its different parts to maturity. For exam- 

 ple, we will suppose two plantations of trees planted at the same 

 time, on similar soil, and in the same climate ; that in the case 

 of the one plantation the soil was trenched and manured, and in 

 the other not ; and that the trees were planted in equal numbers 

 in both plantations, and at the same distances. The trees in 

 the prepared soil would grow rapidly, and in the unprepared soil 

 slowly. After a certain number of years (say twenty), we shall 

 suppose both plantations cut down ; when the timber produced 

 by that which had grown slowly would be found hard, and of 

 good quality ; while that produced by the plantation which 

 had grown rapidly would be found soft, spongy, and, when 

 employed in construction, comparatively of short duration. 

 The reason is, that in this last case the rate of nourishment to 

 the roots exceeded the natural proportion which nature requires 

 in plants, between the supply of food to the roots, and of light 

 and air to the leaves. Had the trees in the prepared soil been 

 thinned out as they advanced, so as never to allow their 

 branches to do more than barely touch each other, they would 

 have produced a great deal more timber than the trees on the 

 unprepared soil, and that timber would have been of equal 

 firmness and duration with timber of slower growth. It ought, 

 therefore, to be strongly impressed on the minds of amateur 

 cultivators, that though nourishment of the root will produce 

 bulk of the top, or, at least, length of top, yet that it is only by 

 abundance of light and air that quality can be secured. 



