50 TRANSPIRATION AND ASCENT OF SAP ch. 



remarkable features in the discussion of the problem 

 of the ascent of sap is that long before these vital 

 hypotheses were conceived, they had received decisive 

 experimental refutation. Boucherie, in 1840, while 

 experimenting on methods of injecting timber for 

 various technical ends, found that if a tree were cut across 

 at the base and supplied with a poisonous fluid, it not 

 only drew this fluid up to its highest leaves, but afterwards 

 would draw up a second solution when the latter was 

 supplied. 



It is strange how the bearing of Boucherie 's experiments 

 appears to have escaped the notice of botanists completely, 

 and it may be noted that Biot, when commenting on 

 Boucherie's work, seems to find no special interest in it 

 in connection with the problem of the elevation of the 

 water of the transpiration current, but occupies himself 

 with other questions. Boucherie's experiments did not 

 wait long for confirmation. A few years afterwards 

 J. Schultz injected trees in the same manner, but his 

 results were also overlooked by botanists. 



It appears, however, to have remained for fStrasburger 

 to point out the full significance of these experiments, and 

 to confirm them with many more of his own, carried out 

 with all possible precautions. 



Strasburger further demonstrated the needlessness of the 

 vital hypotheses by experiments in which stems more 

 than 10'5 metres long, in a vertical position, continued to 

 draw up water after they had been completely killed by 

 exposure to a temperature of 90 C. 



From these results it was abundantly proved that water 

 can rise, and has in these experiments risen, without the 

 assistance of the living cells of the stem; and, if forces 

 exerted by these cells do intervene in raising the water 

 in living plants, they are accessory to, and can only assist 

 the purely physical forces in play which are able to perform 

 the task unassisted. 



