188 Plants. 



The nourishment of plants is perform 

 ed chiefly by the tender fibres of the roots, 

 which being spread under-ground, im- 

 bibe from the moist earth juice fit for 

 their nutriment, which they transmit to 

 the other parts. The impulse by which 

 the juices rise seems to be capillary at- 

 traction ; for the roots of all vegetables 

 are supposed but bundles of capillary 

 tubes : and whether we consider earth, 

 water, salt and oil, as the food of plants - 

 or, with Kirwan, that coal is essential to 

 that food or with Ingenhouz, that it is 

 vital air decomposepl into fixt air and 

 azote ; still that food must be formed by 

 water into an emulsion, capable of being- 

 acted upon by capillary attraction ; and 

 as all roots are but assemblages of these 

 tubes, there can be little doubt but their 

 attraction supplies the plant with its first 

 food ; though other causes must assist 

 in carrying it to the tops of the tallest 

 trees, such as dilatation and contraction, 

 by the successive heat and cold of day 

 and night, the muscular action of vascu- 

 lar rings round the tubes irritated to con- 

 traction by the stimulant sap, &c. The 

 anterior bark conducts the nourishment 

 supplied by the earth. 



