﻿iqi6] CURRENT LIT ERAT L RU 445 



a soil organism which gains entrance through wounds and readily passes from 

 the parent plant to the suckers. It spreads by diseased plants, infected soils, 

 by farm implements, and on the clothing and boots of the laborers.— Mel. T. 

 Cook. 



Permeability.— Stiles and Jorgensen 18 have measured the effect of 

 temperature on the rate at which hydrogen ions of hydrochloric acid are 

 absorbed by the tissue of potato tuber. Disks of potato tubers 1 cm. in diam- 

 eter, weighing about o. 5 gm., were immersed in HC1 of concentration 0.001 1 N. 

 This low concentration was used in order to avoid injury to the tissue. Experi- 

 ments were carried out at temperatures of o°C, io°C, 20 0 C, and 30° C. 

 At intervals up to 8 hours the quantity of the hydrogen ions absorbed was meas- 

 ured by determining the loss of hydrogen ions in the bathing solution. The 

 hydrogen ion content of the latter was measured by a hydrogen electrode, a 

 description of which the authors give. 



The rate of absorption was increased by a rise of io° C. as follows: from 

 o° to 10°, 2. 22 times; from io° to 20 0 , 2.17 times; from 20 0 to 30 0 , 2. 18 times. 

 This is in agreement with the Van't Hoff law for the effect of temperature upon 

 the rate of chemical reaction, and the authors conclude that "the study of the 

 effect of temperature on the absorption of the hydrogen ion would seem to 

 indicate that the absorption is controlled by some chemical action in the cell, 

 and is not the result of simple diffusion through the plasma membrane, or of 

 mere absorption by the cell protoplasm." Their view is that the acid reacts 

 with some substance in the potato, that this substance is either present in 

 large quantity as compared with the amount of acid fixed, or that the resulting 

 compound is broken down again almost as soon as formed. As to the identity 

 of the substance that reacts with the acid, they state it is "presumably the 

 plasma membrane, or some part of it." The reviewer is not convinced yet, 

 however, that in their experiments they were dealing primarily with the 

 permeability of the plasma membrane. The title of the paper expresses the 

 situation more exactly.— F. E. Denny. 



The humidity of a ravine— It has long been commonly accepted that both 

 the atmospheric humidity is greater and the supply of soil moisture more 

 abundant in a narrow ravine than upon the adjacent upland, but no quantita- 

 tive data have been available to confirm these observations. To supply these 

 deficiencies Ullrich 19 measured the evaporating power of the air at 15 different 

 points in a clay ravine, and determined the range of soil moisture for a cor- 

 responding number of stations for a period of four months, from the beginning 



18 Stiles, Walter, and Jorgensen, Ingvar, Studies in permeability. II. The 

 effect of temperature on the permeability of plant cells to the hydrogen ion. Ann. 

 Kotaiu 29:01 1-618. Jigs. 4. 1915. 



