96 Mr G. F. Scott Elliot on the [sess. i.r. 



as heavy on account of its contained air-bubbles. And if we 

 take Hartig's figures, nine volumes of air to ten of water, 

 there is no difficulty in seeing why water should not rise to 

 as great heights as are found in nature. If, on the other 

 hand, the air-bubbles are in contact with the walls of the 

 vessel, their presence is simply an obstruction, and the 

 water will have to get round them by the neighbouring- 

 cells. Boehm's view that the relative tensions of such air- 

 bubbles assists in the elevation of water has been disproved 

 by Zinimermann (27). The surface tension of every bubble 

 must be a resistance' in addition, and the resistance must 

 therefore depend on the number of air-bubbles of Zinnner- 

 mann (27). 



The difficulty of the question is that the premises, namely, 

 the contents of the vessel, at all times of the day, are quite 

 unknown. If we assume that the second view of Vesque 

 and Elfving is correct, we can say that the water rises 

 through the following forces : — first, osmosis {absorbent 

 activity of Vines), both of the cells of the leaf and root; and, 

 secondly, capillarity ; possibly the pressure of the atmosphere 

 may be set down as a third force (Vesque), but we have no 

 data to show what the several influences of these forces may 

 be, and must keep the conclusions open till the premises are 

 satisfactorily settled. 



Literature. 



(1) Vines, Thysiahxj]] of Plants, Cambridge, 1887. 



(2) 8;ichs, PhysioluQV, Eng. ed., 1887. 



(3) Von Hohnel, IMan. Zdt, 1871). 



(4) Scheit, Jena. Zeit., I5d. xviii. and l!d. xix. ; also Botan. Zeit., 

 1884, p. 175. 



(5) Boehm, Botan. Zeit., 1879; also 1881 and 188G. 



(6) Rus.sow, Bot. Centrnltdait, Bd. xiii. p. 29. 



(7) Klobahn, Ber. d. deut. Bot. Ges., 1883, p. 113. 



(8) 8anio, Botan. Ceritral., Bd. xxii. p. 75. 



(9) K. HarLig, Botan. Zeit, 1883. 



(10) Elfving, Botan. Zeit., 1882, \,. 707; also Bot. Centralhlatt, 

 xxi. p. 2G3. 



(11) Volkons, Jitaug. JHsmi., Berlin, 1882. 



(12) Schwendencr, Si.l,z. d. Kon. Preuss. Akad., Bd. xxxiv., 

 18SG ; see BoL CmtirM/att, Bd. xxx. p. 232. 



(13) Ves.pie, Ann. d. Set. Nat., 1884, p. 159. 



(14) Herbert S])eneer, Trans. Linn. Sor., 1866, p. 404. 

 (lb) M'i!^'ab, T/uus. Bot. 8oc. Edin., 1871. 



