224 EXPERIMENT STATION RECORD. [Vol.35 



be entirely impervious to undissolved gases and solids. Consequently the sur- 

 face tension of the sap in the sieve-like pit membranes is not sufficiently great 

 to prevent the penetration of air or gas under the tensile strains that are 

 supposed to occur in tall trees. 



Anatomical and physiolog'ical studies on the aquiferous vessels in plants, 

 II, L. MoNTEMAKTiNi {AtU Ist. Bot. R. Univ. Pavia, 2. ser., 12 {1915), pp. 363- 

 533, pis. 10). — Claiming to have found that the number of conducting vessels in 

 various plants increases from below upward, especially in the neighborhood of 

 branches, and showing also in some cases a certain relation with the develop- 

 ment of surface in the related transpiring organs, the author gives a detailed 

 account of his recent studies on the number and size of the aquiferous vessels 

 and the modifications of the woody elements in relation therewith. 



He sums up much of the extensive data obtained from this work by stating 

 that the quantitative and qualitative modifications which can be noted in the 

 wood at various heights in an organ or system of organs, and which are va- 

 riously combined according to species, individual, or environment, tend on the 

 whole to increase toward the active wood, and more particularly that part which 

 is in more intimate relation with the vascular elements, when measured by the 

 number of the cells which are in direct contact with such elements. Both 

 structure and content in these regions indicate very active changes between 

 the vessels and the cells which surround them. This becomes more and more 

 evident as parts are examined in regions showing greater activity of the tran- 

 spiration stream. 



A bibliography is appended. 



On the permeability of certain nonliving' plant membranes to water, F. E. 

 Denny (Abs. in Science, n. ser., 43 (1916), No. 1105, p. 329). — A report is given 

 of a series of experiments with plant membranes in which quantitative measure- 

 ments were made of their permeability to water. The membranes used were 

 those of the seed coats of peanut, cycad, almond, English walnut, pumpkin, 

 bulb-scale of onion, etc. Results ai-e reported showing the temperature co- 

 efficient for a rise of 10° C, and also showing the permeability of the mem- 

 branes as affected by the concentration of the bathing medium, direction of flow 

 through the membrane, and as influenced by certain chemical constituents of 

 the membrane. 



Studies in permeability. — II, The effect of temperature on the permeability 

 of plant cells to the hydrogen ion, W. Stiles and I. Jokgensen (Ann. Bot. 

 [London], 29 {1915), No. 116, pp. 611-618, figs. J/). — Reporting a continuation of 

 investigations previously noted (E. S. R., 34, p. 731) by methods which are 

 further detailed, the authors claim to have shown that the rate of absorption 

 of the hydrogen ion of hydrochloric acid in dilute solution by potato cells shows 

 a simple exponential relation between time and the concentration of the acid, 

 the absorption rate of potato cells being increased about 2.2 times for each 

 10° C. rise between and 30°. 



The production, by use of parafBin, of hypertrophic and hyperplastic 

 growths in shoots, E. Schilling (Jahrb. Wiss. Bot. IPringsheim], 55 {1915), 

 No. 2, pp. 111-258, figs. JfS). — Giving an account of the anatomical and physio- 

 logical effects of artificially closing the stomata, the author states that the 

 resulting changes observable in the shoot axis are due not to any chemical 

 influence of paraffin or va.spline but to the limitation impo.sed by them upon the 

 tran.spiration process, and perhaps also to the corresponding limitation of oxygen 

 access. It is stated that in the overgrown cells the osmotic pressures are vari- 

 ous but generally higher than in the normal cells. It is claimed also that by 

 covering the surface of the twigs with paruffin, abnormal leaves and adventi- 

 tious roots may be produced. 



