576 SUMMAEY OF CURRENT RESEARCHES RELATING TO 



Action of Ungerminated Barley Diastase on Starch.* — J. L. Baker 

 finds that when the diastase is allowed to act at 50° on a solution of 

 soluble starch, hydrolysis proceeds for an hour to an hour and a half, 

 when a stage is reached beyond which the reaction is comparatively 

 slow. After 1^ to 2 hours dextrin and maltose were the sole products ; 

 after 24 hours evidence of the presence of glucose was obtained, the 

 amount of this sugar apparently increasing in proportion to the time 

 of conversion. Since barley diastase is without action on maltose, the 

 glucose which occurs at the later stage must be derived from the dextrin. 

 This dextrin differs markedly from Nageli's amylodextrin, and in con- 

 sideration of its general behaviour and close relation to the parent 

 starch, the author proposes to call it a-amylodextrin. 



Mosaic Disease of Tobacco, f — A. F. Woods gives an historical 

 summary of the facts relating to this disease, and an account of the 

 results of his own investigations. The leaves of plants attacked by 

 the disease show a more or less sharply defined differentiation into 

 light and dark green areas, giving a mosaic appearance. The light 

 green areas are, as a rule, between the larger vascular bundles, the 

 darker green portions forming a border along the larger bundles. 

 Occasionally, however, the dark and light green patches occur indis- 

 criminately. Where the contrast is more marked the light-coloured 

 areas grow slowly, while the dark green grow more rapidly, and thus 

 the leaf becomes badly distorted. The disease is not due to parasites 

 of any kind, but results from the defective nutrition of the young 

 dividing and rapidly growing cells, due to a lack of elaborated nitro- 

 genous reserve food, accompanied by an abnormal increase in activity 

 of oxidising enzyms in the diseased cells. The unusual activity of 

 enzym prevents the proper elaboration of reserve food, so that a plant 

 once diseased seldom recovers. On the decay of the plant the enzym 

 is set free, and remains active in the soil. It is very soluble in water, 

 and appears to pass readily through plant-membranes. If young plants 

 take it up in sufficient quantity to reach the terminal bud, they become 

 diseased in the characteristic way. Under field conditions there is 

 little danger from infection in this way, but in the seed-bed the danger 

 is much greater owing to the greater susceptibility of the young plants 

 to disease, and the greater amount of free-oxidising enzyms likely to 

 be in the soil due to the decay of roots and plants. New or steam- 

 sterilised soil should therefore be used for the seed-bed. There is 

 evidence that rapid growth, caused by too much nitrogenous manure or 

 too high temperature, is favourable to the disease. 



Action of Hydrogen peroxide on Carbohydrates in presence of 

 Ferrous Sulphate.J — R S. Morrell and J. S. Crofts have continued the 

 investigations of Cross and others, and have shown that dextrose, 

 laevulose, arabinose, and rhamnose are transformed by hydrogen 

 peroxide in presence of the iron salt into osones. 



General. 

 Phyllobiologic Types in some Orders of Seed-Plants. § — Prof. 

 Hansgirg, who has already published an account of his investigations 



* Proc. Cbew. Soc, xviii. (1902) pp. 134-6. 



t U.S. Dept. Agric. Bureau of Plant Industry, Bull. No. 8 (1902) pp. 1-24 

 (6 pis.). t Journ. Chem. Soc„ Ixxxi. (1902) pp. 666-75. 



§ S.B. k. biihm. Ges. Wiss. Math.-naturw. CI., 1901, No. 24, pp. 38. 



