THE HAIRS. 99 



appear sometimes mingled, have each a fixed place: the 

 latter exist upon the parenchjnna, and assist in the 

 evaporation ; the former constantly spring from the veins 

 or their ramifications : but the veins are the parts which 

 least assist in the evaporation; and, consequently, it is 

 not likely that the hairs, which invariably arise from 

 them, serve for this purpose ; we know, on the contrary, 

 that tlie hairs, when they are long or abundant, cover 

 the stomata of the parenchyma, shade them from the 

 action of the solar light, and tend also to diminish its 

 action when it is too intense. Thus we have the reason 

 for a circumstance which appears singular — \iz. that the 

 hairs are almost always placed in plants upon the same 

 surfaces which bear the stomata ; thus, the upper surface 

 of leaves, which most frequently have no stomata, have, 

 in general, few or no hairs; whilst they are usually 

 abundant on the inferior surface, where the evaporating 

 organs are. It would, moreover, be extraordinary to 

 attribute the same use to two such different org-ans — ^to 

 Stomata and Hairs: and, lastly, the other accessory 

 offices which the hairs perform, are all referable to the 

 protection of vegetable surfaces from atmospherical 

 inclemency. 



In several cases, the Lymphatic Hairs serve to protect 

 delicate organs from the coldness of the air : we remark 

 this very e\ddently in the thick down which is found on 

 young leaves when they are enclosed in the buds, or when 

 they are just about to burst forth. Any one can satisfy 

 himself upon this point by inspecting a bud of the 

 Horse-chestnut : these soft, long, and curled hairs retain 

 the air enclosed around these delicate organs, and prevent 

 the access of the external temperature, exactly as the fur 

 of animals ; they fall off or are destroyed usually when 

 the organs have gained more consistence, or when they 

 have passed the critical season. We are acquainted with 



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