OF FOREST-TREES. 37 



grow sickly, and languish without the admission of light as well as air, CHAP, 

 as I have frequently found 



>" If any number of plants are placed in pots in a room which only admits the light by a 

 single hole, the stems will incline, or direct themselves towards that side. In thick 

 forests, the yomig trees always lean to the side where the light penetrates. The new 

 shoots of an espalier detach themselves from the wall which robs them of the air, the sun, 

 and the light. It is in quest of the same excellent gifts of Nature, that the lateral branches 

 of trees, abandoning the direction of the stem, spread and extend themselves in a direction 

 parallel to the soil, even when planted on a declivity. Trunks are not, however, the only 

 parts of plants which direct their course towards the air and the light of the sun. There 

 are flowers, which, quitting their perpendicular direction, present their surface directly 

 to that luminous body, and follow it in its diurnal course. This sort of motion has 

 been called by some writers, nutation ; and the plants which are subject to it, have 

 been termed Heliotropm ; that is, turning with the sun. The story of the Sun-flower, 

 in Ovid's Metamorphoses, is confirmed by daily observation. Thomson beautifully describes 

 its affection : 



But one, the lofty follower of the sun. 

 Sad when he sets, shuts up her yellow leaves. 

 Drooping all night; and when he warm returns. 

 Points her enamour'd bosom to his ray. 



Most of the discous flowers, by some power unknown to us, follow the sun in his course. 

 They attend him to his evening retreat, and meet his rising lustre in the morning with the 

 same constant and unerring law. 



