Reprinted from the Proceedings of the Society for Experimental Biology and Medi 

 cine, 1920, xviii, pp. 95-97. 



44 (1626) 



The specific electrical conductivity of the tissue fluids of desert 



Loranthaceae. 



By J. ARTHUR HARRIS and A. T. VALENTINE. 



[From the Station for Experimental Evolution, Cold Spring Harbor, 



L.I.} 



MacDougal .and Cannon 1 and MacDougal 2 suggested some 

 years ago that the osmotic concentration of the tissue fluids of 

 the two organisms is one of the fundamental variables in the 

 relationship between plant parasite and host. Senn 3 has pub 

 lished one plasmolytic determination indicating higher concen 

 tration in a Viscum than in the leaves of the host tree and has 

 secured similar results with other phanerogamic parasites. In 

 the Jamaican montane rain-forest the concentration of the 

 tissue fluids of the parasitic Loranthaceae is in general higher 

 than those of the host. 4 The same relationship has been found to 

 obtain in desert Loranthaceae. 5 



As far as we are aware the relative electrolyte contents of 

 the tissue fluids of parasite and host have not been determined 

 heretofore. 



In August, 1920, we had the opportunity while carrying out 

 work for the U. S. Department of Agriculture at Sacaton, Arizona 

 to measure the specific electrical conductivity, K, as well as the 

 osmotic concentration in atmospheres, P, calculated from the 

 freezing point lowering, A, of the expressed sap of the leaves of 

 the host trees and of the stems of the leafless Phoradendron cali- 

 fornicum parasitic on the leguminous trees Acacia greggii and 



1 MacDougal and Cannon, Pub. Cam. Inst. Wash., 1910, No. cxxix, P. 3, 25-49. 



2 MacDougal, Bot. Gaz., 1911, Hi, 249-260; Bull. Torr. Bot. Club, 1911, xxviii, 

 54-55. 473-480. 



3 Senn, Verhandl. Naturf. Ges. in Basel, 1913, xc, 179-183. 



4 Harris and Lawrence, Amer. Jour. Bot., 1916, iii, 438-455. 

 Harris, Mem. Torr. Bot. Club, 1918, xvii, 307-315. 



