118 PHYSIOLOGY [Bot. Absts. 



of assuming that leaves are directly connected with the root system by a series of tubes the 

 side walls of which are comparatively impermeable, since otherwise the water would be 

 removed from the tubes by the cells of the stalk, where osmotic pressure is higher than in the 

 leaves. He concludes also that high osmotic pressure is not necessary for the growth of 

 reproductive organs, since both tubers and potato berries (as well as tomato fruits) attract to 

 themselves an abundant supply of reserves, although they maintain a very low osmotic 

 pressure. The factors which control the movement of food reserves is unexplained. The 

 bearing of these investigations on the physiological disease of potatoes known as "tip-burn" 

 is set forth. — E. W. Sinnott. 



801. Shearer, C. The action of electrolytes on the electrical conductivity of the bacterial 

 cell and their effect on the rate of migration of these cells in an electric field. Proc. Cambridge 

 Phil. Soc. 19: 263-265. 1919. — The conductivity of a thick creamy emulsion of the meningo- 

 coccus or B. coli made up in neutral Ringer's solution and measured by a Kohlrausch bridge 

 and cell shows that its resistance is 110 ohms or more than treble that of the Ringer's solution 

 without the bacteria. A bacterial emulsion made of NaCl (0.85 per cent) has a resistance of 

 110 ohms. This gradually drops so that the resistance becomes equal to that of 0.85 per cent 

 NaCl solution without bacteria. KC1, LiCl, and MgCl 2 act like NaCl in reducing the resist- 

 ance offered by bacteria. Bacterial emulsions made up in BaCl 2 , CaCl2, and StCU having 

 the same conductivity as Ringer's solution show no change in resistance for some time, invari- 

 ably remaining normal. Certain trivalent salts have no action in increasing or decreasing 

 the resistance of the bacterial cell as determined by the conductivity method, but affect the 

 rate of migration of these cells in an electric field. — Michael Levine. 



WATER RELATIONS 



802. Shreve, Edith B. Investigations on the absorption of water by gelatin. Jour. 

 Franklin Inst. 187: 319-337. 1919. — Physiological conclusions from the incomplete informa- 

 tion at present available concerning imbibition by jellies are shown to be unwise. The advan- 

 tages and disadvantages of the various methods of measuring imbibition are discussed. The 

 method of weighing was adopted for this work. The rate of imbibition and the total quantity 

 of imbibed water at apparent equilibrium increased with increase of temperature. No true 

 equilibrium seems attainable at any given temperature between 10° and 30 °C, if sufficient 

 time is allowed. In the Hofmeister series all the compounds except sugar caused increased 

 imbibition when incorporated in the composition of the gel preliminary to the imbibition 

 tests. This is quite different from Hofmeister's results when the compounds are in the sur- 

 rounding liquid, for then some do and some do not cause swelling. — Ernest Shaiv Reynolds. 



803. Stewart, E. Grace. Mucilage or slime formation in the cacti. Bull. Torrey Bot. 

 Club 46: 157-166. PL 8. 1919. — A review of views of earlier workers. It appears that 

 opinions are about equally divided as to whether mucilage arises from the wall or from the 

 protoplasm, but several agree that it is accumulated between the plasma membrane and the 

 wall. A study was made of Rhipsalis rhombea, R. pachyptera, R. Houlletiana, Opuntia 

 inermis, and Pereskia Pereskia. In the leaves of flower buds of Opuntia and of Rhipsalis and 

 in the other young tissues mucilage cells are often large and numerous, but their size is not 

 due to imbibition of water by the mucilage; it is due to true growth, and becomes evident 

 before any mucilage formation has begun. The mucilage appears first as a thin film between 

 cell wall and cytoplasm, and as it increases the cytoplasm is crowded in toward the center of 

 the cell, the mucilage becoming alveolar; the cell wall nowhere shows a breaking down. 

 Imbibition experiments show that joints of Rhipsalis swell, particularly in the growing regions, 

 this transformation of cell-contents into mucilage which absorbs water, "may be of importance 

 in conserving and regulating the supply of water for the growing cells themselves." — P. A. 

 Mum. fy 



. MINERAL NUTRIENTS 



804. Purvis, J. E. Bracken as a source of potash. Proc. Cambridge Phil. Soc. 19: 

 261-262. 1919.— See^Bot. Absts. 3, Entry 479. 



