126 EXPERIMENT STATION RECOED. IVol. 38 



The osmotic concentration of tlie sap of plants in the Blue Mountains is the 

 lowest yet extensively investigated, the ligneous forms averaging about 11.44 

 atmospheres and the herbaceous plants averaging about 8.8 atmospheres. These 

 figures are compared with those from other series in other regions. These 

 averages, though the simplest expression of regional differences, are admitted 

 to be not adequately descriptive, as they conceal differences which obtain in 

 each of the areas invsstigated. Further comparisons are to be presented 

 later. 



The relationship between the osmotic concentration of leaf sap and height 

 of leaf insertion in trees, J. A. Harris, R. A. Gobtner, and J. V. Lawrence 

 (Bnl Torrey Bot. Club, U (1917), No. 6, pp. 267-286, figs. ^).— The authors 

 present data obtained from a study of the relationship between the height of 

 insertion of leaves and the physicochemical properties of the leaf sap in trees 

 growing in the open or in the woods. 



Measurements made on 26 trees belonging to 12 species are said to show that, 

 almost without exception, the osmotic concentration of leaf sap (determined by 

 the freezing-point lowering method) increases from lower to higher levels, while 

 specific electrical conductivity shows a tendency, though less regular, to de- 

 crease from below upward. Almost without exception, the ratio of specific 

 electrical conductivity to freezing-point lowering decreases from below up- 

 ward. 



The observed relationship of physicochemical properties to the level of leaf 

 insertion is thought to be due to either internal or environmental factors. The 

 probable bearings of the observed facts are discussed. 



The effect of surface films of Bordeaux mixture on the foliar transpiring 

 power in tomato plants, J. W. Shive and W. H. Mabtin {Plant World, 20 

 (1917), No. S, pp. 67-S6. fig. 1). — Extending the investigations reported by Mar- 

 tin (E. S. R., 36, p. 454), and employing improved methods worked out by 

 Livingston and Shreve (E. S. R., 37, p. 26), but using in this work tomato 

 plants in full bloom which had been grown under agricultural conditions in the 

 open field, the authors state that the indices of transpiring power of the leaves 

 treated with Bordeaux mixture range from 18 to 29 per cent higher than do 

 those of the untreated leaves. The maximum indices in foliar transpiring 

 power for all occiir near the middle of the day, and the influence of the 

 Bordeaux mixture in raising the index is as pronounced when the indices are 

 low as when they are high. 



Permeability of membranes as related to their composition, F. E. Denny 

 (Bot. Oaz., 63 (1917), No. 6, pp. 468-485, figs. 6).— The author describes a study 

 of questions raised in the course of a previous investigation (E. S. R., 38, p. 25) 

 regarding the identity and the relative importance of the substances determining 

 the rate of passage of water through membranes. Seed coats from various 

 economic plants were used. An account is given of factors and treatments 

 influencing permeability. 



The substances affecting the permeability of the membranes to water were 

 lipoids, tannins, and pectic substances. Soluble proteins were not detected. 

 Suberized layers were not significant in this connection. 



Resistance of seed coats of Abutilon theophrasti to intake of water, W. E. 

 Davis (Bot. Oaz., 64 (1917), No. 2, pp. 166, 167).— The results of tests with 

 seeds of A. theophrasti covered with water in stoppered vials in 1910 and re- 

 moved as they were found to have swollen and with seeds collected in 1916 

 from plants standing in the field are said to indicate a wide range in the resist- 

 ing power of the coats of these seeds to water intakes. It is thought that 

 many of the more resistant seeds lie in the soil for many years before 

 germination can take place. 



