'273 VEGETABLE 



parts of the surface with stomata, which Decandolle supposes 

 may act as sucking orifices. Many Mushrooms appear to be 

 capable of absorbing fluids from all parts of their surface in- 

 discriminately ; and some species, again, are furnished at 

 their base with a kind of radical fibril for that purpose. 



lu plants having a vascular structure, which is the case 

 with by far the greater number, the roots are the special or- 

 gans to which this office of absorbing nourishment is as- 

 signed ; but it occasionally happens, that, under certain cir- 

 cumstances, the leaves, or the stems of plants are found to 

 absorb moisture ; which they have been supposed to do by 

 the stomata interspersed on their surface. This, however, is 

 not their natural action ; and they assume it only in forced 

 situations, when they procure no water by means of the roots, 

 either from having been deprived of these organs, or from 

 their being left totally dry. Thus a branch, separated from 

 the trunk, may be preserved from withering for a long time, 

 if the leaves be immersed in water ; and when the soil has 

 been parched by a long drought, the drooping plants will be 

 very quickly revived by a shower of rain, or by artificial 

 watering, even before any moisture can be supposed to have 

 penetrated to the roots. 



It is by the extremities of the roots alone, or rather by the 

 -spongioles which are so situated, that absorption takes 

 place ; for the surface of the root being covered in e very- 

 other part by a layer of epidermis, is incapable of perform- 

 ing this office. It was long ago remarked by Duhamel, 

 that trees exhaust the soil only in those parts which sur- 

 round the extremities of their roots ; but the fact, that ab- 

 sorption is effected only at those points, has been placed 

 beyond a doubt by the direct experiments of Sennebier, 

 who, taking two carrots of equal size, immersed in water 

 the whole root of the one, while only the extremity of the 

 other was made to dip into the water, and found that equal 

 quantities were absorbed in both cases ; while on immers- 

 ing the whole surface of another carrot in the fluid, with 

 the exception of the extremity of the root, which was raised 

 so as to be above the surface, no absorption whatever took 

 place. Plants having a fusiform, or spindle-shaped root, 

 such as the carrot and the radish, are best for these experi- 

 ments. 



The spongioles, or absorbing extremities of the roots, 

 are constructed of ordinary cellular or spongy tissue ; and 



