lOi FUNCTIONS OF LEAVES. 



and becomes loaded with nearly insipid fluids; the sterner 

 juices of the plant previously deposited becoming diluted, so 

 that it is a healthful and agreeable food. This plant, unculti- 

 vated in the manner it is, yields substances exceedingly rough 

 and acrid, and but little corresponding to the mild sweetish 

 stems produced by the gardener's care. This, however, it must 

 be observed, is an immature state of the plant; and the princi- 

 ple of the deposition of carbon by light is used, although empi- 

 rically, in converting an otherwise useless weed to an article of 

 delicacy. We might multiply examples, but one is sufficient to 

 illustrate the principle ; and we may make the remark, which 

 the cultivator would do well to bear in mind, that when plants 

 yield naturally agreeable products, the more light they receive 

 the better they will be ; but when the products, in a state of too 

 great concentration, become acrid, shade will make them more 

 palatable. Of the latter of these is the Radish, and of the for- 

 ni. -r the Potatoe. Hence the Potatoes are much drier, and 

 contain more nutritive matter, which have been grown on open 

 land, exposed to the sun, than those grown in orchards. The 

 truth of these principles is strikingly illustrated also in the geo- 

 graphical distribution of plants. Those of high latitudes, grow- 

 ing through a summer of a few weeks or months, possess few 

 decided properties. They yield the simplest vegetable products, 

 possessing but few properties not common to all vegetables. 

 But as we approach the Equator, the properties become more 

 decided, odors more varied and pungent, fruits more delicious, 

 medicines more powerful and efficient, poisons of the most fatal 

 character, till we arrive at the equatorial regions, where all 

 these products, in all their variety, arrive at perfection. 



184. Forest trees are affected very much by the same prin- 

 ciples. 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 

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

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

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

 turgid with unassimilated fluid. The plant of course bends to- 

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

 the influence the light exerts upon it. We see the same exem- 

 plified in the growth of forest trees. When the forest is dense, 

 light being received entirely on their tops, trees stretch upward, 



Winn should light, and when should Bhade be used '. Hew with plants 

 in high latitudes! Hew La the tropics? 184. How with forest trees? 



Why do plants turn toward the light ? Why do trees grow tall in dense 

 fore'stb I 



