1Q8 AGRIOULTUfiAL ExPEKIMENT STATION, ItHAOA, N. Y. 



processes which contribute to tugescence and in the lesser activity of 

 of those processes which relieve it. 



The most important of these seems to be the excess of root pressure 

 over transpiration. It will be instructive to consider the conditions of 

 environment which have united to disturb the desirable stability of 

 equilibrium of these two forces in the plant. 



The close confinement of the plants in the forcing house where there 

 is little agitation of the air, must necessarily lessen the rapidity and 

 amount of transpiration compared with what would take place in the 

 open. The water vapor freed through transpiration from plants grown 

 in the open under such natural conditions is quickly carried away by 

 currents of air* which are to a greater or less extent in almost constant 

 action. This permits then a more active transpiration than could take 

 place should the water vapor remain undisturbed near the foliar organs. 

 Even should the water vapor escape from the neighborhood of the 

 transpiring surfaces only through the law of diffusion plants in the 

 open would be at a greater advantage than those grown in the confined 

 quarters of the forcing house. That transpiration is obstructed by the 

 humidity of the atmosphere has been abundantly shown. f 



* Sachs Physiology, p. 554. 



Bohnel, Ueber den Geng d. Wassergehaltes iind Transpiration bei Entwick- 

 hmg d. Blattes, 1878. Cited by Pfeflfer, p. 144. 



Wiesner, <^rundver8uche ueber den Einfluss per Luftbewegung auf die 

 Transpiration. Bot. Centralb, viii. pp. 382-383. 



Wind according to Wiesner in most cases accelerates transpiration. In some 

 cases {Saxifraga sarmentosa) it closes the stomates and therefore retards tran- 

 spiration. See same title in P. A. Wein, Abth, i, Bd. xcvi, pp. 182-214. Cited 

 in Just's Bot. Jahrbiicher, 1888, I, pp. 83-84. 



■f-Unger, Sitzungsbericht d. Wiener Akademie, Bd. xUv, 2, 1861. 



Sachs, Handbuch der Experimental-Physiologie, 1865. Sitzungeb. d. Wien, 

 Akad. Bd. xxvi. 



Deherain, Comptes Rendus, T, Ixix. 



Masure, Untersuchungen iiber die Verdunstung des freien Wassers, des im 

 Ackerbodenenthalten Wasser, und iiber die transpiration der Pflanzen, Ann. 

 Agronomiques, T, vi, fasc, iii, pp. 441-500. 



Reinitzer, Ueber die pliysiologische Bedeutuhg der Transpiration der 

 Pflanzen. Sit/.ungsberichte der K. K. Acad, d, Wissenschaft, 1881, I, Abth. 



LeClerc, De la transpiration dans les v6getaux, Ann. d. Sc. Nat. T, xvi, 1883, 

 pp. 231-279. 



Tschaplowitz, Giebt es ein Transpiration-Optimum? Beitrag zur Theoric der 

 Vegetationsconstanten Bot. Zeii. Jahrg, 41, No. 22, S. 353-362. 



Kohl, Die Transpiration der Pflanzen, etc., Braunschweig, 1886. 



Eberdt, Die Transpiration d, Pflanzen und ilire Abhangigkeit von ^usseren 

 Bedingungen , Marburg, 1889. 



Ooodale, Physiological Botany. 



