118 Agricultural Experiment Station, Ithaca, N. Y. 



'^ yperiment farther, but in order to photograph the experiment fresh 

 ^ ' Its were introduced and the photograph was taken ten minutes after 

 p ^ ^ -essure had been turned on. The photograph is reproduced in 

 ^^^ ^^ to show the plan of the experiment and also the numerous 

 drops whic. ^^^^^^^ ^ ^.^^^^ ^^^ leaves of the injected plants, and which 



can be seen ru. . , £ ^-u .. ^„ 



■'ng down on some or the stems. 



The experience hau ^^^^^.^^ ^^^ ^^j^^ ^^^ suggested that, should it 

 ever be repeated, it won., ^^ ^^^^ ^^ ^^^^^ ^ gl^^j. ^^ ^^^ i^rge rubber 

 hose m order to remove all p. ^.^.^^^^ ^^ sediment, since considerable 

 interference arises from the clog^^^g ^f ^1,^ vascular ducts of the 

 cuttings. 



It demonstrates, however, the relation ^^j^ich excessive root 

 pressure* bears to the development of the c ^gj^^Q^g Their appear- 

 ance on the stem of the No. 18 variety through t^e agency of artificial 

 pressure may not seem so convincing perhaps, sinco> this variety was 

 very susceptible to the trouble, and it was quite diffic^ult to obtain a 

 cutting for the experiment which was free from it. 



Their appearance on the stems of the Lorillard variety, the stems of 

 which are much more resistant to the trouble, is quiet conv.-incing that 

 the lack of a proper equilibrium between root and pressure i.^nd trans- 

 piration is an important factor in the cause. 



* It matters little for the present discussion of excessive turgidity \ vhether 



" root-pressure " or the laws governing the lifting of water in the stniems of 



plants is the real cause of the elevation of the water in the tomato ), plants 



beyond the point of the root absorption. It is well known that root prt ^ssure 



cannot lift water to the height attained by some plants and that the trans nira- 



ation current is not the only factor concerned, for it goes on sometimes i. ude- 



I)endently of transpiration. See the following literature: '*■ 



Jamin Comptes Rendus, 1860, 1, pp. 172, 311, 385. " 



Unger, Sitzungsb. d, Akad, d. Wiss. z. Wien. Ivii, 1, 1868. , f* 



Sachs, Vorlesungen fiber Pflanzen physiologic. Ueber die Porositat dP^ea 



Holze, cited by Ward. Timer and some of its diseases, 1889. le 



Boehm. De la cause du movement de I'eau Ann. d. Sci, Nat. 6th ser., T, xii(| 



1881. 



er 

 Elfving, Ueber die, Wasserleitung im Holz. Bot. Zeit. 1882, Oct. ■ , 



Hartig, Ueber die Vertheilung der organischen Substanz, des Wassers i jnd 



Luftraumes in den Bitumen. Unters. a. d. Forst. Bot. Inst. Munchen, 1 .'882. 



Ueber die Ursache der Wasserbewegung in Transpirirenden Pflanzen, I^^bid, 



1883. '■ 



Dufour; Ueber den Transpirationsstrom in Holz-pflanzen, Aarb.d, Bot. loy.nst. 

 Wiirzburg, 1888. ^^^ 



Hartig, Die Gasdrucktheorie und die Saclis' che Imbibitionstheorie, Be rlin 

 1883. Cited by Ward, 1. c. 



