ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 043 



contain mannite. Leaves of Euonymus europeeus produced starch 

 from dulcite, but not from erythrite. Leaves of Cacalia suaveolens 

 obtained it readily and in abundance from glycerin. Experiments 

 with triohymethyls, aldehyd, and organic acids, yielded negative 

 results. 



Formation of Starch out of Glycerin.* — In connection with the 

 experiments of A. Meyer f on the formation of starch, M. E. Laurent 

 has proved the formation of starch in completely etiolated potato- 

 shoots out of glycerin, as well as out of saccharose and glucose; 

 negative results were obtained with acetic acid, oxalic acid, tartaric 

 acid, dextrin, and tannin. With a 10 per cent, solution of saccharose, 

 growth continued more than five months, and tubers containing starch 

 were formed in the axils of the leaves ; with a 5 per cent, solution of 

 glycerin starch- grains were formed in the parenchyma of the stem up 

 to a considerable height. 



Function of Tannin. :£ — Dr. M. Westermaier maintains that tannin 

 in the cells of plants is not a mere waste product of excretion, but 

 possesses assimilating functions, connected especially with the forma- 

 tion of albuminoids. By the action for several days of potassium 

 bichromate, he determined its presence in the palisade-cells of the leaves 

 of a number of plants, also in the conducting tissues, such as the 

 parenchymatous sheath which surrounds the conducting bundles, the 

 conducting cells of the assimilating tissue, and in many elements of 

 the xylem and phloem. Both microchemical reactions and analyses 

 show that the autumnal fall of leaves is preceded by a more or less 

 considerable diminution of the amount of tannin in the palisade-cells. 

 If branch es are ringed, the leaves above the ring contain more tannin 

 at the end of September than the normal leaves in August. In its 

 appearance and translocation, tannin shows analogies with starch. 



Nectar.§ — Dr. A. v. Planta finds that the nectar o£ Protect mellifera, 

 evaporated to a syrup, and thus obtained in large quantities from 

 abroad, contains no nitrogenous matter, but 73 ■ 17 per cent, of solids, of 

 which 70*08 is grape-sugar, and 1*31 cane-sugar. Grape-sugar was 

 obtained from the syrup in a crystalline form. Besides the sugar, a 

 small amount of formic acid (apparently brought by the bees) and 

 ash was present. The following table gives the percentage of sugar 

 in the fresh nectar of three plants examined : — 



Aqueous extracts of various flowers were also analysed ; the small 

 quantity of sugar present in them may be seen from the author's 

 calculation, that in order to obtain 1 gram of sugar (corresponding 



* Bot. Ztg. xliv. (1886) pp. 151-2. t Cf. supra, p. 642. 



X SB. K. Preuss. Akad. Wiss. Berlin, xlix. (1885) pp. 1115-26(1 pi.). 

 § Zeitachr. f. Physiol. Chem., x. (1886) pp. 227-47. 



2 u 2 



