ABSORPTION OF SALTS. 61 



of the substance originally dissolved, it is evident that fifty of those 

 parts must enter the plant, if the absorption of the saline substances 

 be in proportion to that of the solvent. But the experiment proved, 

 that in taking up half the volume of the liquid, the polygonum had 

 absorbed but — 



15 parts of chloride of potassium, 



It follows from these experiments that the plants absorbed some 

 part of the different substances presented to them ; but without ex- 

 ception, they took up the water in greater proportion than the mat- 

 ters dissolved. 



On multiplying and varying these experiments, M. de Saussure 

 always arrived at the same general results. The plants uniformly 

 took up more of the alkaline than of the calcareous salts, and more 

 sugar than gum, though the quantities of the different substances 

 absorbed varied considerably. 



The sulphate of copper presented, in the course of these re- 

 searches, an anomaly which is readily explained. We see that this 

 salt, evidently injurious to vegetation, was taken up in a large dose. 

 This arises from its corrosive action on the roots : sulphate of cop- 

 per disorganizes the spongioles ; and these organs once destroyed, 

 absorption takes place with more rapidity and in greater abundance. 

 A root deprived of spongioles is in the condition of a stalk, or 

 branch, the fresh section of which is immersed in a liquid. Obser- 

 vation proves, in fact, that substances in a state of solution, which 

 by reason of their viscidity are incapable of making their way into 

 a healthy root, are, on the contrary, readily taken up by a cut .stalk 

 or branch, in quantity sufficient to dye it deeply, if it was a coloring 

 matter that was presented for absorption. 



a 



