THE MOVEMENTS AND HABITS OF PLANTS. 31 



radicles of the bean were exposed to the attraction of 

 gravity for an hour or an hour and a half, and their tips 

 were then amputated. Within this time no trace of cur- 

 vature was exhibited, and the radicles were now placed 

 pointing vertically downward ; but an influence had al- 

 ready been transmitted from the tip to the adjoining 

 part, for it soon became bent to one side, in the same 

 manner as would have occurred had the radicle remained 

 horizontal and been still acted on by geotropism. Radi- 

 cles thus treated continued to grow out horizontally for 

 two or three days, until a new tip was reformed ; and 

 this was then acted on by geotropism, and the radicle 

 became curved perpendicularly downward. 



THE POWER OP DIGESTION" IX PLANTS. 



Insectivor- ^ we nave seen ^ na ^ nitrogenous fluids act 



ous Plants, very differently on the leavesof Drosera from 

 page 80. non-nitrogenous fluids, and as the leaves re- 

 main clasped for a much longer time over various organic 

 bodies than over inorganic bodies, such as bits of glass, cin- 

 der, wood, etc., it becomes an interesting inquiry whether 

 they can only absorb matter already in solution, or ren- 

 der it soluble ; that is, have the power of digestion. We 

 shall immediately see that they certainly have this power, 

 and that they act on albuminous compounds in exactly 

 the same manner as does the gastric juice of mammals ; 

 the digested matter being afterward absorbed. This fact, 

 which will be clearly proved, is a wonderful one in the 

 physiology of plants. 



It may be well to premise, for the sake of 

 any reader who knows nothing about the di- 

 gestion of albuminous compounds by animals, that this 

 is effected by means of a ferment, pepsin, together with 



