Physiologie. 251 



ride. For these two salts a pronounced retarding action (15 per cent 

 in both cases), is manifest at low concentrations, the greatest retar- 

 dation occurring with concentration m/128. This retardation in weak 

 Solution seems not to have been considered heretofore. 



Combinations of two salts are shown to be sometimes more and 

 sometimes less effirient in modifying diastatic action than are mo- 

 lecularly equal concentrations of their component salts. It is thus 

 possible that enzymatic power, the magnitude of which is frequently 

 to be related to the concentration of Single salts in the medium, 

 may in some cases at least be still more highly developed than is 

 possible through the influence of Single salts, by the presence of 

 a properly balanced salt combination. Jongmans. 



Kunkel, L. O., A study of the problemofwaterabsorp- 

 tion. (Missouri Bot. Garden- XXIII. Ann. Rep. p. 26—40. 1912.) 



The author discusses the results of his experiments and his 

 studies of the literature on the subject as follows. 



That diffusion enters into the problems of absorption and secre- 

 tion by living cells cannot be doubted, but that F.uch cells maintain 

 their turgor by virtue of osmotic pressure and are surrounded by 

 semipermeable membranes is pure assumption. We can explain 

 turgor and water absorption without assuming the existence of a 

 living membrane possessing the property of semi-permeability. 

 Moreover, such an explanation seems to accord better with facts 

 than does the explanation based on the assumption that such a 

 membrane exists. On the whole, the pressure developed in living 

 cells does not obey the gas laws. In order to keep the osmotic 

 theory of water absorption it is necessary to make various assump- 

 tions regarding the changes in the permeability of the assumed 

 membrane. When we assume that a semipermeable membrane 

 exists, and undertake to become familiär with its properties, we 

 find that the}'^ are not known. The permeability of the same cells 

 seems to be affected differently by different substances. It changes 

 as the concentration of the medium changes and seems to vary, 

 even with the season of the year. The semi-permeable living mem- 

 brane is an assumption, upon which is based a theory, which, it 

 seems to the writer, is not only no longer uscful, but even detri- 

 mental to a correct understanding of the phenomena of absorption 

 and secretion. As Martin H. Fisher has pointed out, we know 

 very little regarding the afifinity between colloids and watery Solu- 

 tions. We use the word "affinity" to cover our ignorance, but it 

 seems better to do this than to make an assumption that does not 

 find justification in the facts that are known. Jongmans. 



Livingston, B. E. and W. H. Brown. Relation of the daily 

 march of transpiration to variations in the water 

 content of foliage leaves. (Bot. Gazette. Uli. p. 309-330. 1912.) 



The writers conclude from their measurements and comparisons 

 that there can remain little question that green plants when subjected 

 to relatively great diurnal evaporation intensity, at least frequently 

 exhibit a marked fall in foliar moisture content by day and a 

 corresponding rise by night. The daily march of evaporation remains 

 still to be studied in other climates than that of summer in southern 



