372 THE UNIVERSE. 



sorption is an essentially vital phenomenon, and we share in 

 the most unqualified manner this opinion of the greatest 

 botanist of modern times, which was also that of Senne- 

 bier, Saussure, and Desfontaines. 



To the suction of the spongiole, which ceases as soon 

 as life is extinguished, are accessorily joined some purely 

 physical forces, such as endosmosis, capillary attraction, and 

 hygroscopic action, which some naturalists have erroneously 

 looked upon as the special agents of it. 



The radicles seem to select instinctively from the soil the 

 food of the plant, which is scattered through it, just as out 

 of the midst of the nourishment which fills the intestine 

 in animals the chyliferous vessels pump up only the fluid 

 which is to regenerate the organism. Like the latter, the 

 spongioles of plants are sometimes deceived, and introduce 

 along with the sap some poison which kills them. But ab- 

 sorption is so little left to the chemico-physical powers that 

 certain plants vegetate in soil charged with deadly sub- 

 stances without suffering in the least from it. In the coun- 

 tries where arsenic abounds there are some which brave its 

 corrosive action. Hence, when everything else is dying 

 round them, certain leguminous plants cover with verdure 

 the rocky soil of Cornwall, which contains fifty per cent, of 

 arsenical sulphuret, while the rest of it consists of silica and 



sulphuret of iron. 1 



By means of very simple experiments it can be demon- 

 strated that absorption by the roots is a vital act. If, on 



1 According to Dr. Daubeny, professor at Oxford, the sulphuret of arsenic, con- 

 tained in small quantities in the soil, produces no injurious effect upon mustard, 

 beans, and barley. He concludes that, to a certain extent, plants possess the 

 power of selecting from the constituents of the soil in which they live. 



