INSTANCES OF LEAVES ROOTING. 



275 



When plants' are produced by leaves under ordinary circum- 

 stances, the conditions most favourable to their doing so are of 



Pig. XXXVIII.— Booting leaves of a, Gesnera; 6, CUantliuspiimceus; c, Gloxinia speoiosa. 



the same nature. A moderate amount of moisture prevents 

 their dying from perspiration or perishing from decay ; a good 

 bottom heat stimulates their vital forces, and causes them to 

 exercise whatever power they possess ; and, in addition, they 

 are covered by a slightly shaded bell-glass, which maintains 

 around them an atmosphere of uniform humidity, and, at the 

 same time, cuts off the approach of those direct solar rays, 

 which, acting as a stimulus to perspiration, would have a 

 tendency to exhaust the leaves of their fluid before they could 

 organise, at their base, the new matter from which the leaf-bud 

 is eventually produced. 



The rationale of this operation seems to be as follows. 



T 2 



