6 THEPHILOSOPHY 



fuifaces are covered with a number of minute glands, which fe- 

 crete a fweet liquor, and allure the approach of flies. When thefe 

 parts are touched by the legs of a fly, the two lobes of the leaf in- 

 ftantly rife up, the rows of prickles lock themfelves faft together, 

 and fqueeze the unwary animal to death. If a ftraw or a pin be 

 introduced between the lobes, the fame motions are excited. 



When a feed is fown in a reverfed pofition, the young root turns 

 downward to enter the earth, and the ftem bends upward into the 

 air. Confine a young ftem to an inclined pofition, and its extre- 

 mity will foon aflume its former perpendicular direSion. Twift 

 the branches of any tree in fuch a manner that the inferior furfaces 

 of the leaves are turned toward the Iky, and you will, in a fhort 

 time, perceive that all thefe leaves refume their original pofition. 

 Thefe motions are performed fooner or later, in proportion to the 

 degree of heat, and the flexibility of the leaves. Many leaves, as 

 thofe of the mallow, follow the courfe of the fun. In the morning, 

 their fuperior furfaces are prefented to the eaft ; at noon, they 

 regard the fouth ; and, when the fun fets, they are direded 

 to the weft. During the night, or in rainy weather, thefe leaves 

 are horizontal ; and their inferior furfaces are turned toward the 

 earth. 



What has been denominated the Sleep of Plants, affords an In- 

 ftance of another fpecies of vegetable motion. The leaves of many 

 plants fold up during the night ; but, at the approach of the fun, 

 they expand with renewed vigour. The common appearances of 

 moft vegetables are fo changed in the night, that it is difficult to re- 

 cognife the difTerent kinds, even by the affiftance of light. 



The modes of folding in the leaves, or of fleeping, are extremely 

 various. But it is worthy of remark, that they all difpofe them- 

 felves 



