212 PHYSIOLOGY [Bot. Abbts., Vol. 1V 5 



lytes on the conductivity of electrolytes in special reference to conductivity measurements of 

 plant juices. The author ascribes the low results obtained in such measurements to the 

 mutual action of non-electrolytes and salts, but does not discuss the nature of the action. A 

 study is also made of the results of Dixon and Atkins on frozen and unfrozen tissues — the 

 author finding there is little evidence for the marked differences which they assume to exist 

 in the proportional composition of the two saps. A formula is suggested by which, in certain 

 cases, conductivity measurements may be reduced to standard conditions. — A. R. Davis. 



1408. Shull, C. A. Permeability. [Rev. of: Free, E. E. A colloidal hypothesis of pro- 

 toplasmic permeability. Plant World 21 : 141-150. 1918. Bot. Gaz. 68: 70. 1919.— This new 

 hypothesis as to the nature of permeability and changes in permeability seems to the reviewer 

 less objectionable than any previously proposed; it should stimulate research, since definite 

 testing seems possible. — H. C. Cowles. 



1409. Ursprung, A. Uber den Einfluss der Erwarmung auf die Wasseraufnahme unter- 

 getauchter Sprosse. [On the influence of rise in temperature on the water absorption by sub- 

 merged plants.] Ber. Deutsch. Bot. Ges. 36: 514-528. 1918. — Experiments carried on with 

 shoots of Fag us and Thuja show that an increase in the temperature of the water, in which the 

 shoots are immersed, has at first no effect on water absorption, and often causes a movement 

 in the opposite direction. This is followed by a sudden rise in the absorption curve, then a 

 decrease, and finally a cessation of the movement of water. The decrease, observed by 

 immersing the shoots in water, may be due to the expansion of the air in the vessels. The fol- 

 lowing rise in the absorption curve is probably due to the activity of the living cells. These 

 cells may at first absorb a small amount of the air in the vessels, thereby producing a nega- 

 tive pressure; however, the amount of air absorbed could only be small and would not account 

 for the sudden rise of the absorptive curve. The explanation may well be sought in the 

 increased absorbing power of the living cells, accompanied by a change in the permeability of 

 the plasma membrane when the temperature of the surrounding medium is increased.— 

 Ernst Artschwager. 



1410. Ursprung, A., and G. Blum. Zur Kenntnis der Saugkraft II. [Contribution to 

 our knowledge of the suction force.] Ber. Deutsch. Bot. Ges. 36: 577-599. 1918. — The method 

 for measuring the suction force of cells is previously described (Ber. Deutsch. Bot. Ges. 34: 

 525). The material was left in the solution (0.2 M cane sugar) for a definite time, usually one 

 hour. In order to save time in calculating the results, the threshold concentration was deter- 

 mined for two decimals only. Only mature leaves were examined, all of them coming from a 

 single plant, Hedera, which was kept under the same environmental conditions throughout 

 the experiment. The following values (expressed in atmospheres) were obtained: lower epi- 

 dermis 5.6-8.4, upper epidermis 7-8.7, upper palisade 8.7-16.4, spongy parenchyma 7.3-12.4, 

 bundle sheath 7.3-9.3, collenchyma 7.3-8.1, guard cells 7.15-13.7, parenchyma of petiole 6.7- 

 9.3, upper stem 4.2-7.4, lower stem 2.1-3.3, ray cells 2.1-2.6, root 0.8-3.2. — Ernst Artschwager. 



1411. Ursprung, A., and G. Blum. Besprechung unserer bisherigen Saugkraftmes- 

 sungen. [Discussion of earlier results on suction phenomena.] Ber. Deutsch. Bot. Ges. 36: 

 599-618. 1918. — The pressure increases from the vascular tissue toward the epidermis. The 

 highest pressure is found in the upper palisade layer. The epidermis gives lower values. The 

 guard cells have a relatively higher pressure than the adjacent epidermal cells. The paren- 

 chymatous bundle sheath has a slightly lower value than the epidermis, which would enable 

 the latter tissue to obtain water that could not be obtained through the palisade cells which 

 always have a higher pressure. It becomes apparent that the palisade tissue and the spongy 

 parenchyma obtain the water directly from the water-conducting elements and draw on the 

 supply in the epidermis only when the water content sinks "very low. As a rule, the suction 

 force of a tissue increases with its distance from the roots, and in a given cross section of an 

 organ the pressure increases with an increase in the distance from the water-conducting tissue. 

 The one exception is the epidermis of the leaf lamina and this makes it possible that in 

 times of need the palisade cells can draw on the water reservoir of the epidermis. — Ernst 

 Artschwager. 



