^9181 AGRICULTUEAL BOTANY. 



523 



detenniued by air circulation. The term relative humidity is rejected as its 

 use is criticized. . o ito 



The index of atmospheric evaporating power should equal the product of the 

 mdex of circulation by the index of the moisture condition, all measurements 

 having been properly weighted and brought into correspondence in deriving the 

 indices. " When it is not desirable or expedient to employ the index of atmo.s- 

 pheric evaporating power itself (as determined directly by some form of 

 atmometer), the moisture condition of the air should be stated in terms of the 

 vapor pressure deficit, which demands no correction for air temperature and 

 may represent evaporating power in all comparisons where the index of effec- 

 tive air circulation may be considered as constant." 



Atinometric units, B. E. Livingston (Johns Hopkins Univ. Circ, n. scr 

 No. 3 (1917), pp. i60-i70).— Summarizing a discussion of atmometers and their 

 employment, the author states that every atraometric measurement should be so 

 formulated as to include all of the features, location, period of operation, units 

 of water lost per unit of time, and type of atmometer. If any of these features 

 is lacking, the expression for the atmometric reading has no intelli-ible 

 meaning. " 



A simplified apparatus for measuring the conductivity of electrolytes 

 R. P. HiBBAKD (Rpt. Mich. Acad. Sci., 18 (1916), p. 49).— This is a brief exposi- 

 tion of the work previously noted (E. S. R, 34, p. 732), and of the features 

 characterizing the modifications in apparatus and technique employed. 



A simplification of the present freezing' point method for the determina- 

 tion of the osmotic pressure of plant sap, O. E. Hakuington and R. P Hib- 

 BARD (Rpt. Mich. Acad. Sci., 18 (1916), pp. 47, 4S).— The work here briefly noted 

 and reported on previously (E. S. R., 36, p. 823) was done upon fleshy tissues. 

 Further work is considered necessary to test the applicability of the method 

 to drier tissues. 



Selective permeabiUty and the plasma membrane, J. Davidson (Plant 

 World, 19 (1916), No. 11, pp. 331-349 ).-Fvom the opinions and evidence here 

 discussed the author concludes that the data available regarding the existence 

 of special plasma membranes in plants are too indefinite and indirect to war- 

 rant any conclusions at the present time, so that the term plasma membrane as 

 now used may refer to the entire cytoplasm as well as to a special membrane. 



There is no adequate method of testing the permeability of living cells. The 

 accepted explanation of plasmolytic phenomena, it is thought, may be incor- 

 rect notwithstanding its plausibilits'. 



The influence of an incomplete culture solution on photosynthesis, O. M, 

 Gruzit and R, P. Hibbaed (Rpt. Mich. Acad. Set., 18 (1916), pp. 50-52).— The 

 studies here briefly noted, which were intended to determine what influence is 

 exerted upon so-called vital activities of plants (especially photosynthesis) by 

 an incomplete culture solution, were carried out in the greenhouse during the 

 month of February. 



The results, whicli are tabulated, are considered to show that the dry weight 

 per unit area of leaf surface of seedlings is less for those grown in a complete 

 solution than for those grown in a solution which lacks one component. The 

 assumption that a large amount of photosynthate in leaves indicates energetic 

 growth is not borne out. Solutions which lack potassium, calcium, and phos- 

 phorus show relatively great gains in weight, but this is not considered as 

 indicating metabolic efficiency in plants grown in solutions lacking these ele- 

 ments. It is suggested that the explanation lies in a reduced translocation and 

 a retarded photosynthesis. Tests with cucumber seedlings in the various solu- 

 tions show that the increase in dry weight of detached leaves exceeds consider- 

 ably that of attached leaves. The greatest gain occurred in the complete sola- 



