548 APPENDIX II. 



Askenasy's theory may also be maintained, as is more nearly shown in 

 his treatise, on the assumption that the tracheal channels contain not only 

 water, but a moderate amount of low tension air. If, however, much air 

 penetrates into the channels of conduction, e.g., when structures are cut 

 off in the air, then a rapid passage of water into the objects is rendered 

 impossible, and they wither, although placed with the cut surface in 

 water. 



See Askenasy, Verhandlungen d. naturhistorisch-med. Vereins zu Heidelberg, N.F., B. 5. 

 See Sachs, Lectures on Plant Physiology. 



See Hansen, Arbeiten d. botan. Instituts in Wurzburg, B. 3, p. 312. 



See Strasburger, Bau und Verrichtung der Leitungsbahnen in den Pjlanzen, 1891, p. 808. 

 See Russow, Botan. Centralblatt, 1883, B. 13, p. 101, and Strasburger, Leitungsbahnen, 

 p. 685. 

 6 On the quantity of air in the wood, see Strasburger, Leitungsbahnen, p. 682. 



