114 FUNCTION OF LEAVES. 



substances exceeding rough and acrid, and but little corres- 

 ponding to the mild, sweetish stems produced by the garden- 

 er's care. This, however, it must be observed, is an immature 

 state of the plant ; and the principle of the deposition of car- 

 bon by light is used, although empirically, in converting an 

 otherwise useless weed to an article of delicacy. We might 

 multiply examples, but one is sufficient to illustrate the prin- 

 ciple, and we may make the remark, which the cultivator 

 would do well to bear in mind, that when plants yield natur- 

 ally agreeable products the more light they receive the better 

 they will be ; but when the products, in a slate of too gieat 

 concentration become acrid, shade will make them more palat- 

 able. Of the latter of these is the Radish, and of the former 

 the Potatoe, Hence the potatoes are much drier and con- 

 tain moro nutritive matter, which have been grown on open 

 land exposed to the sun, than those grown in orchards, which 

 is often the case. The truth of these principles is striking- 

 ly illustrated also in the geographical distribution of plants. 

 Those of high latitudes, growing through a summer of a few 

 weeks or months, possess (ew decided properties. They 

 yield the simplest vegetable products, possessing but few 

 properties not common to all vegetables. But as we a])proach 

 the equator, the properties become more decided, odors more 

 varied and pungent, truits more delicious, medicines more 

 powerful and efficient, poisons of the most fatal cliaracler, till 

 we arrive at the equatorial regions where all these products, in 

 all their variety, arrive at perfection. 



141. Forest trees are afiected very much by the same princi- 

 ples. The wood of dense forests is known not to be as firm, or as 

 durable as that of trees growing in open grounds. We see also 

 the effect of these principles in the turning of plants towards 

 the light when it comes to them in only one direction. The 

 side next the light deposits its carbon, and becomes firmer, 

 harder, and of course contracted, while the other side remains 

 turgid with unnssimilated fluid. The plant of course bends 

 towards the light, not from any attraction it has for it, but 

 from the influence the light exerts upon it. We see the same 

 exemplified in the growth of forest trees. When the forest 

 is dense, light bei.ig received entirely on their tops, trees 

 stretch upwards, the lower branches decay, and thus forming 

 tall, straight cylindrical trunks, with the branches near their 

 summit. Trees in open fields never grow as tall as in forests, 

 but they have a greater number of branches, and nearer to 

 the earth ; and the reason is plain from the foregoing remarks ; 

 they, receive the direct rays of the sun at every difTerent po- 



