512 Theory of the Nutrition [BOOK in. 



up together, the weeping of severed root-stocks and the rise of the 

 sap in the wood in transpiring plants. The first is caused, he 

 thinks, by impulsion, the other by attraction; we should now say, 

 that in weeping root-stocks the water is pressed upwards, in trans- 

 piring plants drawn up. He then refers the phenomenon of im- 

 pulsion to endosmose in the roots, and without going much into 

 detail as regards the anatomical conditions, he compares a 

 weeping root-stock to his own endosmometer, in the tube 

 of which the fluid that has been sucked in rises by endosmose 

 and even flows over ; it is true that no very thorough under- 

 standing of the matter was gained in this way, but at any 

 rate the principle which was to explain it was indicated. 

 He then endeavours to explain the movement of the water 

 which ascends in the wood of transpiring plants by the action 

 of endosmose from cell to cell. In this he failed entirely, 

 as was afterwards perceived ; but he succeeded in showing 

 that all the mechanical explanations that had been previously 

 attempted were incorrect, and the whole treatise, though 

 unsatisfactory in its main result, contains a great number of 

 ingenious experiments and acute remarks. 



With the exception of Theodore de Saussure, who occupied 

 himself exclusively with chemical questions in physiology, 

 Dutrochet was the only vegetable physiologist in the period 

 between 1820 and 1840 who studied all its more important 

 questions thoroughly and experimentally; his treatise on the 

 respiration of plants, which has been already mentioned, is 

 excellent in itself, and was of the greatest importance at the 

 time it appeared, because it brought the chemical processes in 

 respiration, the entrance and exit of the gases, for the first time 

 into correct connection with the air-passages in the plant, with 

 the stomata, the vessels, and the intercellular spaces, and sub- 

 mitted the composition of the air contained in the cavities of 

 plants to careful examination. It was the best work on the 

 respiration of plants in the year 1837 and for a long time after ; 

 and if Dutrochet made the mistake of regarding the oxygen 



