134 CARNEGIE INSTITUTION OF WASHINGTON. 



obtained by pressing untreated tissues can not be considered typical 

 of the whole sap of the tissue. The authors show that there is a 

 gradual increase in concentration in successive fractions of the expressed 

 plant-sap. 



Harris and Lawrence have also studied the plant-sap in relation to 

 environment on the Arizona deserts, to determine the crj'-oscopic 

 constants. For the region as a whole the average cryoscopic determin- 

 ants are: trees and shrubs, 28.10 atmospheres; dwarfs and half shrubs, 

 27.45 atmospheres; perennial herbs, 16.35 atmospheres; winter annuals, 

 14.73 atmospheres. In relation to habitat the concentration of plant- 

 juices increases in the following series: arroyos, Pima Canon, rocky 

 slopes, mesa-Uke slopes, salt-spots. 



TABLE OF OSMOTIC PRESSURE BASED ON DEPRESSION OF FREEZING-POINT. 



Dr. Harris has extended a table of osmotic pressures of vegetable 

 saps, based on depression of the freezing-point, from 3.00 to 5.99. 



STUDIES IN PERSONAL EQUATION AND STEADINESS OF JUDGMENT. 



Dr. Harris, as results of his biometric work, has published two papers 

 in the Psychological Review, entitled, "Experimental data on errors of 

 judgment in the estimation of the nmnber of objects in moderately 

 large samples, with special reference to personal equation" (Nov. 

 1915), and "On the influence of previous experience on personal equa- 

 tion and steadiness of judgment in the estimation of the number of 

 objects in m.oderately large samples" (Jan. 1916). He reaches the con- 

 clusion that errors in estimation (in the case of 50 beans) are due, 

 among other things, to personal equation and steadiness of judgment. 

 In three subjects — 



"There is a slight but significant personal equation, which, notwithstanding 

 the constant efforts to improve, persists throughout the two years during which 

 the experiments were intermittently made. For a measure of steadiness of" 

 judgment is used the coefficient of variation. The subjects differed more 

 strikingly in steadiness of judgment than in personal equation. 



"Personal equation seems to be remarkably little influenced by experience. 

 In some exj^eriments it increases, in others it decreases. 



"Steadiness of judgment is in rather conspicuous contrast with personal 

 equation in that it is remarkably influenced by previous exjDerience. The 

 correlations between the number of previous trials within the period and 

 steadiness of judgment and between the number of previous periods vrithin 

 the experiment and steadiness of judgment are numerically Ioav, but almost 

 without exception indicate that as experience becomes greater the scattering of 

 the individual estimates about their mean value becomes less. Probably the 

 rate of this change is not uniform, but is most rapid at first and then falls off." 



BIOMETRIC MISCELLANY. 



The correlation between a series of measures taken in one year and a 

 series taken a subsequent year may be designated as direct interannual 



