88 



CARNEGIE INSTITUTION OF WASHINGTON. 



The sodium cell connected with a suitable portable galvanometer 

 offers many advantages for measurement of light intensities in natural 

 habitats. It seems highly probable that more exact measurements in 

 the blue-violet region, so important in photolysis and phototropism, 

 will yield information by which some of the current discordant results 

 may be harmonized. In any case, the action of the photo-electric cell 

 in hght is more nearly parallel to that of the organism than that of any 

 other Ught-measuring instruments hitherto available. (Science, n. s., 

 vol. XLV, No. 1172, pp. 616-618, June 15, 1917.) 



ECOLOGY AND PHYTOGEOGRAPHY. 



Osmotic Concentration of Tissue Fluids in relation to Geographical Distribution, 



by J. Arthur Harris. 



Ciyoscopic studies at the Desert Laboratory in 1914 (Carnegie Inst. 

 Wash. Year Book, 1915, p. 81, and 1916, p. 79) confirmed the con- 

 clusions of Drabble and of Drabble and Fitting by showing that the 

 osmotic concentration of the sap of plants may differ in the local 

 habitats of a region. Since then these studies have been extended to 

 a number of very diverse areas. At present, the ultimate object of 

 these investigations is the completion of a reconnaissance of the sap 

 properties of the vegetations of typical phytogeographical regions. 

 The regions in which fakly comprehensive series of observations have 

 been made are the follov/ing: 



1. Southwestern deserts in the neighborhood of the Desert Laboratory, which have been 



studied in both winter and summer growing-seasons. Studies in the winter have 

 of necessity been limited to the desert floor. Those made in the summer have 

 ranged from the Laboratory domain through all the remarkable transitions of 

 environmental conditions and vegetation to the summit of the Santa Catalina 

 Mountains. 



2. The coastal deserts of the Island of Jamaica. 



3. The mesophytio region about the Station for Experimental Evolution, Long Island, 



New York. 



4. The pineland and Everglades hammocks of southern Florida. 

 .5. The montane rain forest of the Blue Mountains of Jamaica. 



