The Suction-force of Transpiring Branches \ 
BY 
S. H. VINES. 
O F all the still incompletely solved problems of the 
physiology of plants, none has received so much 
attention of recent years as that of the means by which 
a current of water is maintained in a lofty tree between the 
absorbing roots on the one hand, and the transpiring leaves 
on the other. Without entering upon a discussion of all the 
various theories which have been proposed to account for this 
fact, it may be pointed out briefly that, according to prevalent 
opinion, it cannot be satisfactorily explained on the imbibi- 
tion-theory of von Sachs 2 , nor on the gas-pressure theories of 
Hartig 3 and Boehm 4 , nor on the vitalistic theory of God- 
lewski 5 ; and that it is not merely a phenomenon of capillarity. 
It would appear, from the researches of Dixon and Joly 6 and 
of Askenasy 7 , that the motive power is the suction-force of 
1 I have published a brief note on this subject in the last (June, 1896) numler 
of the Annals, p. 292. 
2 Vorlesungen ueb. Pflanzenphysiologie, 2 te Aufl., 1887, p. 221. (Eng. Ed., 
p. 241.) 
3 Die Gasdrucktheorie, 1883. 
4 Warum steigt der Saft in den Baumen, Wien, 1S78; also Ann. d. sci. nat., 
ser. 6, t. 6, 1878. 
5 Pringsheim’s Jahrblicher, XV, 1884. 
6 Annals of Botany, Vol. viii, 1894; Proc. Roy. Soc., Vol. lvii, 1895; Phil. 
Trans., 1895. 
7 Verhandl. d. naturhist.-med. Vereins zu Heidelberg, Neue Folge, Bd. v, 1895 
and 1896. 
[Annals of Botany, Vol. X. No. XXXIX. September, 1896.J 
