AGRICULTURAL BOTANY. 825 



The presence and physiological significance of tannin in plants, C. van 

 WissELiNGH (Bot. Ccntbl, Beihefte, 32 (1915), 1. Abt, No. 2, pp. 155-217, pis. 

 2). — The author describes researches carried on by himself with Spirogyra 

 maxima as regards tannin. It is claimed that this plant contains a substance 

 closely allied to gallotannin in the cell sap, and that the precipitate obtained 

 by the use of certain bases Is a tannin and not a nitrogen product. Antipyrin 

 and caffein have proved to be well adapted to the demonstration of tannin in 

 living cells without injury thereto. 



It is thought that in case of S. maxima the tanin present in the cell sap 

 is not an excretion product or a reserve material, but a solute in process 

 of utilization by the plant along with other dissolved substances. 



Correlations appear to exist between tannin and other bodies, as chromato- 

 phores and starches. 



Elaioplasts in monocotyledons and dicotyledons, I. Politis (Atti 1st. Bot. 

 R. Utiii-. Pa via, 2. scr., 12 {1915), pp. 345-SoO). — The author claims to have 

 found elaioplasts in 27 species representing 19 genera of monocotyledons, 

 and in the Malvacete among the dicotyledons. They are to be regarded 

 as the specific organs of the cell which are concerned with the elaboration of 

 oily material. Elaioplasts are regarded as fundamentally similar in substance 

 to the nucleoli. In bulbs, it is stated, new elaioplasts are formed with each 

 resumption of vegetative activity. 



The electrical conductivity of sap in vegetable tissues, Eva Mameu (Atti 

 1st. Bot. R. Univ. Pavia, 2. set:, 12 {1915), pp. 285-297).— The author shows 

 that successive degrees of torsion or pressure to which the tissues of Opuntia 

 ficiis indica and of Agave americana were subjected gave corresponding in- 

 crea.ses in the conductivity of the expressed sap. 



In case of Diotostemon hookcri. Aloe grandidcntata, and A. africana, per- 

 mitted to dry slowly at from 16 to 20° C, the specific conductivity diminished 

 at first, but later increased. In case of the last two of these and of A. striata, 

 it appears that the specific conductivity decreases with the age of the organs. 



In O. flciis indica and Agave sp., the specific conductivity of leaf tissue from 

 the basal region exceeded that from the apical portions. 



Studies on wilting, drying, and returgescence of plants, H. Holle {Flora 

 [Jena}, n. ser., 8 {1915), No. 1-3, pp. 73-126, figs. 6).— The author has studied 

 various plants as to the conditions in the vascular elements in wilting or drying 

 shoots, the changes in living parenchyma cells while drying out, the relations 

 of air to drying cells, and the restoration of turgor, including the influence of 

 temperature in this connection. He has also considered some implications of 

 water movement theories. 



It is stated that in the neighborhood of wounds the concentrating cell sap 

 withdraws water from the uninjured cells. The cell membranes shrink with 

 the diminution of the cell contents. The shrinking of the cell wall is noted 

 in dead as well as in live cells. Small, gas-filled spaces may appear in the 

 parenchyma cells as they dry, but they do not restore the form of the crinkled 

 cell membrane. Thin walled parenchyma cells show no such bubbles, being 

 squeezed together in a compact mass. While dead cells are losing their water, 

 cohesion tensions are set up of various degrees of intensity before the gas 

 bubbles appear. Penetration of membranes by air in case of pressures of one 

 atmosphere or less does not occur so long as the cell is filled with water. 

 Restoration of turgor in detached shoots occurs in warm water somewhat more 

 quickly than in cold, within certain limits of resistance of the cut surface. 



A bibliography is appended. 



Some relations of plants to distilled water and certain dilute toxic solu- 

 tions, M. C. Meebill {Ann. Missouri Bot. Gard., 2 {1915), No. 3, pp. 459-506, 



