No. 1, August, 1920] PHYSIOLOGY 117 



static effects of the ions present and that tin* influence of ions on the osmotic pressure m 

 be the same as that on the initial velocity of diffusion. This assumption was pul to a test 

 in experiments with gelatin salts for which a collodion membrane is strictly semipermeable 



;m<l the tests confirmed the expectation." — 0. /•'. Curtis. 



850. Shull, C. A. Permeability. [Rev. of: William.-, M aid. The influence of immer- 

 sion in certain electrolytic solutions upon permeability of plant cells. Ann. Botany 32 : 591 690. 

 1918. (See Bot. Absts. 2, Entry 304.)] Bot. Gaz. 68: 232. 1919. 



S51. Stiles, Walter, and Franklin Kidd. The comparative rate of absorption of var- 

 ious salts by plant tissue. Proc. Roy Soc. London 90 B: 487-504. Tables 1-10, fig. 1-7. 1919. 

 — Rate of absorption of various chlorides, sulphates, nitrates, and potassium salts from solu- 

 tions 0.02N was measured by the electrical conductivity method, using discs of carrot and 

 potato. — Initial absorption was rapid, possibly in proportion to ionic mobility. This is 

 followed by a long period of almost logarithmic approach to equilibrium. The final quantity 

 absorbed is independent of the initial rate in the case of any given salt. — Initial adsorption 

 rates are in the following order: Rations, K (Ca, Na), Li (Mg, Zn), Al; anions, SO\», N0 3 

 CI. — The final absorption order is, kations, K, Na, Li (Ca, Mg) ; anions N0 3 , CI, SO*. Mon- 

 ovalent ions are at equilibrium in much greater quantity than divalent ions in the cases stud- 

 ied. The rate and extent of intake of one ion of a salt may be affected by the nature of the 

 other ion. From aluminium sulphate aluminium is rapidly absorbed, and the sulphate ion 

 slowly. — It is pointed out that there is essential agreement with other workers. — Paul B. 

 Sears. 



852. Thoday, D. The "osmotic hypothesis:" a rejoinder. New Phytol. 18: 257-259. 

 1919. — This is an answer to certain criticisms brought forward by Stiles and J0rgensen. — 



1. F. Lewis. 



WATER RELATIONS 



853. Cribbs, James E. Ecology of Tilia americana. I. Comparative studies of the foliar 

 transpiring power. Bot. Gaz. 68: 262-286. 13 fig. 1919. 



854. Dosdall, Louise. Water requirement and adaptation in Equisetum. Plant World 

 22 : 1-13, 29-34. 5 fig. 1919.— See Bot. Absts. 4, Entry 217. 



855. Flood, Margaret G. Exudation of water by Colocasia antiquorum. Sci. Proc. 

 Roy. Dublin Soc. 15 : 505-512. 2 pi. 1919. — An inquiry into the question of whether the water 

 exuded from the leaf-tips of Colocasia was conduction water, or whether it was secreted 

 from a special gland led to the following considerations: 1. It had been related to transpira- 

 tion and called a nocturnal "liquid transpiration" supplanting the diurnal vaporous one. 



2. The drops were sometimes seen to be ejected for short distances, coming through small 

 pores. 3. It had been stated that the water was secreted by a hydathode and that the secre- 

 tion was simple filtration. 4. Modern observations had shown that the freezing point of the 

 exudate differed little from distilled water, and that its electrical conductivity was less than 

 that of tap-water. — A colloid (India ink mixed with gelatine) was successfully passed through 

 the end pore and up into the canals, after some preliminary experimentation. When the leaf- 

 tip was attached to a water reservoir, after severance from the leaf, drops of water continued 

 to be exuded. This amounted to 6 cc. in 20 hours. These experiments (and the last-men- 

 tioned repeated, substituting a0.3 per cent starch solution) prove that there was no continuous 

 membrane between the depression and the water channels. Anaesthetizing the tip did not 

 slow up the rate of dropping, showing that the water must be urged forward from below in 

 the plant and not exuded by the action of the tip alone. Cutting the leaf-blade anywhere 

 results in copious exudation from the veins at every cut. The same occurs when the petioles 

 are cut. The conclusions from these observations and experiments, made when the soil about 

 the plant was damp and the air saturated, is that no gland or epithem functioning in secretion 

 is present in the leaf-tip. The phenomenon must depend upon the normal transfer of water 

 through the plant. [See also Bot. Absts. 4, Entry 1406.]— A. E. Waller. 



