Phvsioloirie. 1S7 



'e> 



Zuckerrüben, Gerste, Kartoffeln und Weizen. 5 Abbildungen zei- 

 gen das. 



Die Tafeln, die infolge ihrer charakteristischen Wiedergabe 

 der Nährstoffmangel-Erscheinungen z.T. schon in einige neuere 

 Lehrblicher übergegangen sind, tragen in hohem Masse dazu bei, 

 auch in nicht wissenschaftlichen Kreisen den Nutzen der künstli- 

 chen Düngung den Interessenten klar vor Augen zu führen. Es 

 wäre erwünscht, wenn bald noch weitere Versuche in dieser vor- 

 züglichen Weise bildlich festgehalten und in Buchform verbreitet 

 würden. H. Klenke. 



Reed, G. B., Th oxidasesofacid tissues. (Botanical Gazette 

 LVII. p. 528—530. 1914.) 



From the writers paper it is evident that Citrus fruits have 

 normal oxidases in their acid tissues. It is also evident that these 

 oxidases are protected in some manner from the action of the acid 

 which at this concentration etfectually inhibits the action of oxidases. 

 It seems to the writer that this protection may be afforded by a 

 semipermeable surface (the plasma membrane or cell walls similar 

 to the cell walls of barley seed, which are impermeable to acid) 

 through which the acid is unable to pass. When the tissue is ground, 

 previous to pressing out the juice, the structure which. separates 

 the acid from the ferment is destroyed, so that the action of the 

 later is inhibited. That these membranes are not normally perme- 

 able to acid is shown b}' the fact that seeds of lemon (which are 

 separated from the acid by the walls of the sacs) frequently ger- 

 minate while still in the carpels, though they will not germinate in 

 lemon juice several times dilutcd. 



It seems probable that this condition is a general one in acid 

 tissues. The acid and ferment are separated in the tissue probably 

 in a variety of ways, but the grinding destroys the separating sur- 

 face, bringing acid and ferment in contact and inhibiting the action 

 of the latter. M. J. Sirks (Haarlem). 



Shaw, H. B., An improved cog Psychrometer. (PI. World. 

 XVII. p. 183—185. 2 figs. 1914.) 



An Instrument is described for ascertaining relative humidity 

 in restricted areas, as among foliage, in small frames. etc. 



E. S. Johnston. 



Shive, J. W., The freezing points of Tottingham's nu- 

 trient Solutions. (Fl. VVorfd. XVII. p. 345-353. 1914.) 



An experimental determination of the osmotic concentrations or 

 diffusion tensions, by means of the Beckmann method of free- 

 zing point lowering, of the nutrient Solutions employed by T ot- 

 tin gh am (Physiol. Res. I. p. 133—245. 1914), who approximated 

 diffusion tensions by a method of calculation, which considered 

 that each Salt of a complex mixture ionizes to the same degree as 

 though the other salts were not present. Tottingham's calculated 

 diffusion tensions were for series L, 0,05, for series IL, 2,50, and 

 for series III., 8,15 atmospheres. The cryoscopic method gave va- 

 lues in practical agreement for series I, but an average value of 

 2,528 atmospheres for series 11.^ and an average value of 7,22 at- 

 mospheres for series III. Only in this last (supra-optimal) series are 

 the deviations marked. Sam F. Trelease. 



