AGRICULTURAL BOTANY. 27 



The phenomona of change in living structures are said to apply to organisms 

 in general, and this hypothesis, it is believed, will afford an explanation of a 

 number of more recent observations on plant metabolism. 



Investigations regarding the phloem and food conduction in plants, F. U. 

 G. Agrelius (Kans. Univ. Sai. Bui, 5 (1010), No. 10, pp. 169-179, pis. 2).— 

 A special study has been made of the devices for the transfer of food materials 

 in the phloem of vascular plants, comparisons studies being made of the phloem 

 in stems, petioles, and fruit stalks, of 72 species of plants, representing 65 genera 

 and 39 families. 



The siiecial devices for the lateral transfer of food present in the phloem and 

 cortex of plants are said to be the pitted cells, the arrangement wf the phloem 

 in narrow wedges, and the radially elongated medullary-ray cells which are 

 especially adapted to conduct the food. The second device was found to be the 

 sieve tubes, and they were demonstrated in all but three of the plants examined. 



Phototaxis, assimilation, and growth, P. A. Dangeabd (Bui. Soc. Bot. 

 Fmiicc, 57 (1910), 7\'o. 5, pp. 313-31!)). — A resume is given of observations on 

 the influence of light on various organisms, in which certain greenish colored 

 bacteria were found to arrange themselves in definite parts of the spectrum. 



A brief account is also presented of a method of determining the assimilation 

 of various species of algje through the liberation of oxygen, and the effect of 

 various colored screens corresponding to definite portions of the spectrum on 

 the growth of alg:e is described. 



Metabolism and translocation in young conifers, H. Bauer (Naluno. 

 Ztschr. Forst u. Landw., S (1910), No. 10, pp. /i57-Ji9S). — The results are given 

 of a chemical investigation into the metabolism and translocation takiilg place 

 in coniferous seedlings. Larch, hemlock, fir, and pine seedlings were used in 

 the experiments, and the variation of their nitrogen and principal inorganic 

 constituents was determined, analyses being made at 4 different periods, which 

 corresponded to the times when growth was just beginning, when the new 

 organs were beginning to appear, at the full height of growth, and at its au- 

 tumnal cessation. The results are given in tabular form. 



The morphology of leaf fall, E. Lee (Ann. Bot. [London], 25 (1911), No. 

 97, pp. 51-106, pis. 3, figs. 20). — The results are given of an anatomical study of 

 various species of dicotyledonous plants, in which an attempt was made to 

 determine the morphology of leaf fall. 



It was found that in dicotyledonous plants the essential modification at the 

 leaf base in connection with leaf fall is the formation of a separation layer 

 which is produced from existing cells with or without division. The leaf 

 separates from the stem by the disappearance of the middle lamellae of the 

 cells of the separation layer and the subsequent rupture of the sieve tubes and 

 vessels of the leaf trace. A lignified layer may or may not be present, but a 

 protective layer is invariably produced either before or after leaf fall. This 

 protective layer is formed by ligno-suberizatiou of the cells of the leaf base, or 

 of cells produced by the continued division of a regular cambium. The pro- 

 tection of the tissues of the stem underlying the leaf scar is aided at a later 

 date by the production of a layer of cork cells. 



In many species the persistent leaf or leaf scar is thrown off during the 

 second year. 



Becent investigations on the glucosid of pear leaves and its role in au- 

 tumn coloration, E. Bourquelot and Mlle. A. FtCHTENHOLz (Jour. Pharm. et 

 Chim., 7. set:, 3 (1911), No. 1, pp. 5-13; Compt. Rend. Soc. Biol. [Paris], 69 

 (1910), No. 38, pp. 605-607).— Subsequent to their discovery of a glucosid, arbu- 

 tin, in pear leaves (E. S. R., 24, p. 31), the authors have examined leaves of a 

 considerable number of species that have been referred to the genus Pyrus 



