2 SCIENTIFIC PROCEEDINGS (112). 



shown to be necessary by Dixon and Atkins 8 and others. 9 His 

 constants are, therefore, as pointed out by Atkins, 10 probably sub- 

 maximum because of incomplete extraction. 



Work on the spring flora of the Arizona deserts 11 was probably 

 carried out in a manner to obviate the objections to the preceding 

 studies. In this series the maximum concentrations were found 

 in Atriplex canescens, a shrub of the salt spots, in which A = 5.65, 

 P = 67.5, and in Mortonia scabrella, a small shrub of the mesa- 

 like slopes, for which one determination gave A = 4.78, P = 57.2. 



Concentrations of about fifty atmospheres have been demon 

 strated in the leaf tissue fluids of more or less sclerophyllous trees 

 Capparis ferruginea and Guaiacum officinale and in those of the 

 succulent-leaved halophytic half shrub Batis maritima of the saline 

 coastal flats of Jamaica. 12 Cryoscopic studies on mangrove 

 vegetation 13 have indicated maximum concentrations of about fifty 

 atmospheres in Avicennia nitida, although two questionable 

 determinations indicated seventy atmospheres. Using plasmo- 

 lytic methods, von Faber 14 reports concentrations ranging from 24 

 to 72 atmospheres in East Indian species of the mangrove asso 

 ciation. 



During the summer of 1920, while engaged in field operations 

 in collaboration with the Department of Agriculture in the Great 

 Salt Lake region, we had the opportunity of making several 

 hundred determinations of the osmotic concentration of plant 

 tissue fluids by the cryoscopic method. These measurements 

 were made on sap extracted after freezing of the tissues 15 and with 

 such care as to render the results reasonably free from criticism. 

 Such a series, based on species which have for ages been subject 

 to the influence of the highly saline substratum afforded by the 



s H. H. Dixon and W. R. G. Atkins, Proc. Roy. Dublin Soc., 1913, N. S., xiii, 

 422-433. 



9 R. A. Gortner, J. V. Lawrence, and J. Arthur Harris, Biochem. Bull., 1916, v, 

 139-142, pi. i. 



10 W. R. G. Atkins, &quot;Some Recent Researches in Plant Physiology,&quot; London, 

 1916, 94. 



11 J. Arthur Harris, J. V. Lawrence, and R. A. Gortner, Phys. Res., 1916, ii, 

 1-49. 



12 J. Arthur Harris and J. V. Lawrence, Bot. Gaz., 1917, Ixiv, 285-305. 



13 J. Arthur Harris and J. V. Lawrence, Biol. Bull., 1917, xxxii, 202-211. 



14 F. C. von Faber, Ber. Deutch. Bot. Ges., 1913, xxxi, 277-281. 



16 R. A. Gortner and J. Arthur Harris, PI. World, 1914, xvii, 49-53. 



