6 



ANALOGY BETWEEN PLANTS AND ANIMALS, 



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 dis- 

 tances : the trees in the prepared soil would grow rapidly ; and in the un- 

 prepared 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 gi'own 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 more timber than the trees in 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 at the same time. 



12. One very remarkable point of difference between animals and plants 

 is that which has been before alluded to, viz., the much greater provision 

 which nature has made for the propagation of the latter than of the former. 

 Plants not only produce immense quantities of seeds, which are distributed 

 by the winds and waters, by animals, and hy various causes ; but they ex- 

 tend themselves by shoots, which run on or under the surface of the ground, 

 as in the case of the strawberry, the raspberry, &c. ; and they produce buds, 

 each of which, by human art, can be rendered equivalent to a seed, either 

 by planting it (with a small portion of the plant from which it is taken) at 

 once in the ground, or by inserting it in another plant of the same family. 

 Hence, the great facility with which plants are multiplied both by nature 

 and art ; with the exception of a few, in which the process of propagation by 

 artificial means is comparatively difficult. 



13. Another remarkable difference, also before alluded to, between plants 

 and animals, is, the absolute necessity of light to plants during the whole 

 period of their existence. There are many animals of the lower description, 

 such as worms, to which light, so far from being necessary, is injurious; and 

 there are instances of even the more perfect animals having lived for several 

 years without the presence of light, either natural or artificial. Light is not 

 necessary for either the functions of the stomach, brain, or lungs, in animals ; 

 but in plants, though it is equally unnecessary for the functions of the ger- 

 minating seed, the root, and the collar, it is essentially so for those of the leaves ; 

 and the leaves are necessary to the elaboration of the sap, and, consequently to 

 the nourishment of the plant, A plant, therefore, from which the leaves are con- 

 tinually stripped as soon as they are produced, soon ceases to live. Small and 

 weak plants, from which the leaves are taken off as they are produced, will die 

 in a single season ; and this practice, continued for two seasons, will kill, or 

 nearly so, the largest tree. If, instead of stripping a plant of its leaves, the 

 leaves are produced in the absence of light, and light never admitted to them, 

 the effect will be precisely the same. Seeds germinated, or plants struck from 

 cuttings, in the dark, will not exist a single season ; nor will trees, or tubers, 

 such as potatoes, placed in an apartment from which all light is excluded. 



