ii 4 TRANSPIRATION AND ASCENT OF SAP ch. 



struction of cohesion, countless numbers of minute ruptures 

 have been simultaneously produced. 



Experiment No. 8 gives the details of a third observation 

 with this tube. 



The tubes S a and S 2 were filled with boiled sap of Fagus 

 silvatica, which was, however, subsequent to boiling, ex- 

 posed in a thin layer to the air ; while the tubes S 3 and 

 S 4 , on which Experiments 7, 8, 9, and 10 were performed, 

 contained unboiled sap of Ilex aquifolium. 



In Experiment 3, after the bubble had been " closed ' 

 at a temperature of 63, the tube was maintained at 

 about 61 for two days. During this time no rupture 

 appeared. 



The foregoing shows that the sap of trees has consider- 

 able tensile strength, and in this respect does not differ 

 from water. In the few experiments made, the ease with 

 which tension was generated and its magnitude before 

 rupture occurred, possibly indicate that sap is somewhat 

 more stable under tension than pure water. 



Literature. 



Berthelot, M. , " Sur quelques phenomenes de dilatation forcee des liquides," 

 Ann. de Phys. et de Ghim. 1850, 30, p. 232. 



Dixon, H. H., "Note on the Tensile Strength of Water," Proc. Boy. 

 Dublin Sue. 1909, vol. xii (N. S.), p. 60, and Notes from The Botanical School, 

 Trinity College, Dublin, vol. ii, p. 38. 



Id. " Vitality and the Transmission of Water through the Stems of Plants," 

 Proc. Roy. Dublin Soc. 1909, vol. xii (N. S.), p. 21, and Notes from the 

 Botanical School, Trinity College, Dublin, vol. ii, p. 58. 



Id. " On the Tensile Strength of Sap," Proc. Boy. Dublin Soc. 1914, vol. 

 xiv (N. S.), p. 229. 



Dixon, H. H., and Joly, J., "On the Ascent of Sap," Phil. Trans. Boy. 

 Soc. London, 1895, vol. 186 B, p. 568. 



Id. "The Path of the Transpiration Current," Ann. of Bot. 1895, 9, 

 p. 404. 



Donny, J., "Sur la cohesion des liquides et sur leur adhesion mix corps 

 solides," Ann. de Phys. <! ('him. 1846, 16 Ser. iii, p. 167. 



Evvart, A. J., "Resistance to Flow in Wood Vessels," Ann. of Botany, 

 1905, vol. 19, p. 442. 



Johonnot, E. S., " Thickness of the Black Spot in Liquid Films," Phil. 

 Mag. 1899, No. 289, p. 50]. 



