ORGANS OF DIGESTION. 89 



spongelets are obstructed, and the plants are suffocated, 

 or rather perish of famine in the midst of plenty. 



The spongelets will not in any case admit of the 

 smallest particle of a solid substance. Sir H. Davy 

 mixed with water some charcoal so finely powdered 

 as to be impalpable, in a phial where a plant of pepper- 

 mint was growing. During a fortnight the plant grew 

 vigorously ; yet on cutting the roots in different parts 

 not a trace of the black powder could be detected. 



Though the spongelets of the roots, however, are in 

 most cases the main inlet of nourishment to plants, 

 there are also suckers in other parts, particularly on 

 the under sides of the leaves of trees, for when Bonnet 

 and Du Ham el placed leaves with their under sides 

 on water they kept long green, while they soon 

 withered when placed on their upper sides. But 

 this might be from the evaporation of their leaf 

 pulp being prevented, as much as from moisture 

 sucked up. 



Plants deprived of their regular supply of carbon- 

 ised water, have resources which are very remarkable. 

 Thus a shoot cut from a tree and either end planted, 

 will take in water at the cut ends of its vessels, till 

 new rootlets furnished with spongelets are formed. 

 Upon this is founded the practice of propagating 

 plants by cuttings 1 . 



The root, however, is the regular organ, and when a 

 leaf or the cut end of a shoot in the process of striking, 



0) This is further explained in the "ALPHABET OF SCIENTIFIC 

 GARDENING," p. 72, &c. 



