Transpiration and the Ascent of Sap. \P) 



this latter mig-lit rise by the mere suction of these cells to a height 

 of 15 m in the form of a Ja m in 's chain. 



Strasburger ^) in reply followed up and confirmed his experi- 

 ments by one on an oak nearly 22 ra high. It was sawn obliquely 

 across at its base and then set upright in water, where it remained 

 half an hour. During this time its surface was cleaned and smoothed 

 with a sharp knife and then set in a saturated solution of picric 

 acid. The tree drew up the picric acid for 3 days. On the 4 th 

 day, when the picric acid was found at a height of 15 m and the 

 appearance of the topmost leaves had marked]}' changed, fuchsin was 

 added to the picric acid supply. After running 8 days and 16 hours 

 the experiment was stopped and the tree investigated. The highest 

 branch was completely impregnated with the picric acid which had 

 consequently been drawn up to the height of 21*8 m over the surface 

 of the supply. Also he found at this level patches coloured with 

 fuchsin showing that the solution of fuchsin had been taken up into 

 the wood although preceded by the picric acid by 3 days. This con- 

 clusive experiment demonstrated that watery solutions can rise in trees, 

 without the assistance of the living cells in the regions traversed, 

 to heights far above those to which atmospheric pressure and the 

 capillary forces of the tracheal tubes could raise them. In passing 

 it may be pointed out that, inasmuch as the bubbles cannot move 

 past the partitions dividing up the conducting tracts into vessels and 

 tracheids, a moving water-column, at any rate, must be regarded 

 as continuous round the bubbles and as exerting its full hydrostatic 

 pressure. Consequently it is quite illegitimate to assume that normal 

 atmospheric pressure could raise water in plants in the form of a 

 J a m i n 's chain above 1033 m. 



Strasburger-) further demonstrated the needlessness of the 

 vital hypotheses by experiments in which stems over 10*5 m long in 

 a vertical position continued to draw up water after they had been 

 completely killed by exposure to a temperature of 90*^ C. A summary 

 of these important experiments will be of interest and is given on 

 p. 16. 



From these results it is 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. 



') E. St ras burger, Ueber das Saftsteigen. Jena 1893, pp. 10 et seq. 

 ^) E. Strasburger, Ueber den Bau und Verrichtungen der Leitungsbahnen 

 in den Pflanzen. Jena 1891, pp. 645 et seq. 



