Maech 3, 1916] 



SCIENCE 



329 



tioned tehaved in a manner similar to the primary 

 roots, reacting more promptly in media offering 

 considerable resistance to penetration than in 

 looser media. In the ease of secondary roots the 

 lack of complete permanent georeaction in moist 

 air, as contrasted with prompt and complete curv- 

 ature in earth, seems to be due to the mechanical 

 cause mentioned above in connection with primary 

 roots. 



On the Permeability of Certain Non-living Plant 

 Membranes to Water: F. E. Denny. 

 A report of a series of experiments with plant 

 membranes in which quantitative measurements 

 were made of their permeability to water. Mem- 

 branes used were seed coats of peanut, cycad, al- 

 mond, English walnut, pumpkin, bulb-scale of 

 onion, etc. Measurements were made in an osmom- 

 eter so constructed as to detect the passage 

 through the membrane of very small quantities of 

 water, and to keep the physical factors such as 

 temperature and concentration of solution con- 

 stant. In each test the exact area of membrane 

 used was known. Results are reported showing 

 the temperature coefficient for a rise of 10° C, 

 and showing the permeability of the membranes 

 as affected by the concentration of the bathing 

 medium, direction of flow through membrane, and 

 as influenced by certain chemical constituents of 

 the membrane. 



Influence of Temperature on the Moisture Intake 



of Seeds: Chaeles A. Shull. 



A critical analysis of the data obtained as lo 

 the rate of moisture intake by seeds possessing 

 semipermeable coats (XantMum) at various tem- 

 peratures from 5 degrees to 50 degrees O. shows 

 that the curve of intake is by no means so simple 

 as was assumed by Brown and Worley for barley 

 seeds. The curves of intake are essentially the 

 same In character in certain seeds used, whether 

 semipermeable coats are present or not, but differ 

 in steepness according to the kind of seed used. 

 The temperature coefficient for the rate of intake 

 is decidedly lower than the Van't Hoff coefficient 

 for chemical processes, and considerably lower 

 than the values obtained with barley seeds. More- 

 over, plotting the logarithms of hourly rate of in- 

 take against temperatures does not yield straight 

 lines. It is evident, therefore, that the conclusions 

 reached by Brown and Worley are not applicable 

 generally. 



Some Experiments on Galvanotropism: C. H. Fare. 

 (Introduced by E. A. Haepee.) 



The Structure of the Bordered Pits of Conifers 

 and Its Bearing upon the Tension Hypothesis of 

 the Ascent of Sap in Plants: I. W. Bailey. 

 The tension hypothesis of the ascent of sap in 

 plants, as interpreted by Dixon, postulates continu- 

 ous columns of water that are entirely free from 

 bubbles (0.02 mm. or more in diameter) of air or 

 gas. However, even if continuous columns of 

 water are present throughout the year, which has 

 not been demonstrated conclusively, it remains to 

 be shown how high tensions can arise and be main- 

 tained in the tracheids of tall trees. The pit 

 membranes of Conifers are not entire septa, and 

 are not impervious to undissolved gases and solids, 

 as has previously been supposed to be the case. 

 They are porous or sieve-like in structure, and the 

 surface tension of the sap, in the sieve-like pit 

 membranes of various Conifers, is not sufficiently 

 great to prevent the penetration of air or gas, 

 under the tensile strains that are supposed, by 

 Dixon, to occur in tall trees. 



H. H. Baetlett, 



Secretary 



SOCIETIES AND ACADEMIES 



THE BIOLOGICAL SOCIETY OF WASHINGTON 



The 546th meeting of the Society was held in 

 the Assembly Hall of the Cosmos Club, Saturday, 

 December 4, 1915, and called to order by President 

 Bartsch at 8 P.M. with 55 persons present. 



On recommendation of the council Dr. E. W. 

 Shufeldt, Washington, D. C, and Arthur deC. 

 Sowerby, Tien Tsin, were elected to active mem- 

 bership. 



On recommendation of the council the following 

 resolutions were read and adopted: 



Wheeeas: Dr. George M. Sternberg, former 

 Surgeon General of the U. S. Army, a distin- 

 guished worker in the biological sciences as ap- 

 plied to medicine, long time an active member of 

 the Biological Society of Washington and its 

 president during the years 1895 and 1896, has 

 passed from this Ufe, therefore be it 



Sesolved: That the Biological Society of Wash- 

 ington keenly regrets his death and offers its 

 warmest sympathy to Mrs. iSternberg, and will al- 

 ways be grateful to his memory for the important 

 part which he took in the affairs and discussions of 

 the society and for the distinction which his 

 eminent name adds to its list of past presidents. 

 Signed L. O. Howaed, 



FeEDEEICK V. C'OVILLE, 



Paul Baetsch 



