148 SARRACENIA. 



moved, cuttings, grafts, &c. and on the other hand the 

 benefit of heat and air to promote due perspiration 

 and evaporation. 



The perspiration of aquatic plants seems to be re- 

 markably copious. Of these some grow constantly im- 

 mersed in the water, as most species of Potaynogeton, 

 Pond-weed, Engl. Bot. t. 1G8, 297, 376, &c. Their 

 leaves are peculiarly vascular, and dry very quickly in 

 the air, withering in a very few minutes after exposure 

 to it. Their absorbing power seems equally great, so 

 that they appear to be continually, in their natural 

 situation^ imbibing and giving out a quantity of water 

 much greater than has been observed in land plants. J| 

 Other aquatics^ like the Nijjnphcea, Engl. Bot. t. 160, ^ 

 lloat with only the upper surface of their leaves ex- „ 

 posed to the air, which surface is so contrived that '^ 

 water will scarcely remain upon it. These leaves, 

 though extremel}^ j^icy, dry with great rapidity, as 

 does every part of the plant when gathered. It is 

 probable that they imbibe copiously by their under 

 sides, and perspire by the upper. 



The oeconomy of the Sarracenia, an American ge- 

 nus of which we now know four species, and of the 

 East Indian Nepenthes distillatoria, deserves particu- 

 lar mention. Both grow in bogs, though not absolute- 

 ly in the water. The former genus has tubular leaves 

 w hich catch the rain like a funnel and retain it ; at 

 least such is the nature of S, purpurea, Curt. Mag. 

 t. 849^ whose ma>'gin seems dilated expressly for this 



