1917] AGRICULTUBAJL BOTANY. 433 



of the four substaBces in the soils depend on the fact that the compounds serve 

 as sources of food for different species of bacteria. 



Studies in permeability. — IH, The absorption of acids by plant tissue, 

 MiLDKED Hind (Ann. Bot. [London^, SO (1916), No. 118, pp. 22S-238, figs. 11).— 

 Tliis is a continuation of the series of studies begun by Stiles and Jorgensen 

 (E. S. R., 35, p. 224). The present author has attempted to ascertain how far 

 the rapid absorption of hydrogen ions, as previously noted in regard to hydro- 

 chloric acid in aqueous solution, is charactertistic of acids in general. Several 

 acids were used in this work, which was carried out with potato tubers and 

 with living plants of Yicia faba. The part played by proteins was also studied. 



It was found that the hydrogen ions of all the acids examined are rapidly 

 absorbed by plant tissue from dilute solutions. The anion largely determines 

 the effect of the acid on the cell, the fatty acids contrasting strongly with the 

 mineral acids in this respect. Proteins may also influence acid absorption by 

 plants. Lecithin was not shown to be concerned in such absorption. 



Production of root hairs in water, Ethel M. Bakdell (Univ. Wash. Pubs. 

 Bot., 1 (1915), No. 1, pp. 9). — The author, outlining exx)erimental work on root 

 hair development in water in the case of sunflower, maize, pea, bean, wheat, 

 oats, and Tradescantia, states that elongation of root cells is greater in air than 

 in water. The number of root hairs tends to decrease with increase of strength 

 of the fractional solutions of normal potassium nitrate, this being ascribed to a 

 decrease of absorption and consequent diminution of turgor. 



The conclusions of Snow (B. S. R., 17, p. 849) have been confirmed by the 

 employment of other methods. It is stated that Light conditions do not affect 

 root hair production. Curves and swellings favor the production of root hairs, 

 which are more abundant on the concave side of curves. Usually cortical cells 

 in hairy portions are shorter than those in hairless portions, also the average 

 length of hairy cells grown in air, water, or fractional solutions of normal 

 potassium nitrate is usually less than that of hairless epidermal cells and of 

 cortical cells. 



A n:iethod for maintaining a constant volume of nutrient solutions, O. L. 

 Claek (Science, n. ser., U (1916), No. 1146, pp. 868, 869, fig. 1).—A method for 

 the automatic renewal of nutrient solutions is briefly described. 



Proposed classification of the genus Kollinia, with descriptions of several 

 new species, W. E. Saffobd (Jour. Wash. Acad. Sci., 6 (1916), No. 12, pp. 370- 

 S8Jf, figs. S). — In an attempt to correct what are considered errors of classifi- 

 cation, the author has made a revision of available material which is con- 

 sidered to belong to the genus Rollinia, from which certain forms have been 

 previously set apart by him under the generic name Rolliniopsis (E. S. R., 36, 

 p. 220). 



Desmopsis, a new genus of Annonaceae, W. E. Saffokd (Bui. Torrey Bot. 

 Club, 4S (1916), No. 4, pp. 188-193, pis. 3, fig. i ) .—Technical descriptions are 

 given of species to which the new generic name Desmopsis is given, under the 

 specific names D. panamensis, D. galeottiana, D. maxonii, D, bibracteata, and 

 D. oerstedii. 



Pleiospermium, a new genus related to Citrus, from India, Ceylon, and 

 Java, W. T. Swingle (Jour. Wash. Acad. Sci., 6 (1916), No. 13, pp. 426-431).— 

 A new genus, Pleiospermium, is described to include the species formerly 

 known as Limonia alata and L. dubia. These species, which are technically 

 described, are suggested as suitable stocks for Citrus, the former on the drier 

 soils, the latter on limestone hills. It is thought that, on account of its primi- 

 tive and polymorphic nature, P. dubium may hybridize with some true citrus 

 species. 



