478 SUMMARY OF CURRENT RESEARCHES RELATING TO 



6. When completely dried and then swollen again in a moist 

 atmosphere and again dried, wood contracts less than when quite 

 fresh, but shows a greater volume than fresh wood similarly dried. 



6. From these facts it is shown that when wood is but slightly 

 dried the molecular structure of the walls undergoes no change, but 

 that changes take place as soon as the desiccation is more complete. 

 It is not therefore possible to infer the quantity of water imbibed by 

 the cell-walls of wood in the fresh condition, from the imbibition of 

 wood dried at 100° C. 



Carbonates in Living Plants.* — MM. Berthelot and G.Andre have 

 estimated the amount of soluble and insoluble carbonates in the root, 

 stem, leaves, and flowers of different plants, at different stages of their 

 growth; the analyses are given in detail. Fresh plants contain a 

 certain amount of free carbon dioxide produced by internal oxidation. 

 In the root, leaves, and flowers, the carbon dioxide is mainly in the 

 free state, while in the stem it seems to exist entirely in the form of 

 carbonates. 



Relation of the "Vegetable Acids to Assimilation.t — Using De 

 Vries's curcuma-test for the presence of vegetable acids in parts of 

 plants, Herr O. Warburg has determined that in succulent plants the 

 two processes of the formation and disappearance of the acids are 

 going on at the same time, the increase or decrease of these sub- 

 stances depending on their relative energy. Thin-leaved plants show, 

 as a rule, no difference in the amount of acid by day and by night. 

 Plants with dry leathery leaves show, on the contrary, a small diminu- 

 tion by day ; this being much more considerable in most succulent 

 plants, as Crassulacese, Aloineae, EuphorbiaceEe, and StapeliesB (some 

 AsclepiadeaB and Compositse form an exception), and still greater in 

 the epiphytic OrchidesB and Bromeliacese. Experiments on etiolated 

 plants and on normal plants under coloured media, show that assimila- 

 tion and the disappearance of acids are dependent on the same con- 

 ditions, the latter being much the strongest with the least refrangible 

 rays of the spectrum. The author infers that the acids are used up 

 in a kind of intramolecular assimilation. The abundance of acids in 

 succulent plants is due to imperfect oxidation. The acid present in 

 largest quantities appears to be malic acid. 



Assumed Bacterian Origin of Diastase.^ — M. E. Laurent has put 

 to an experimental test the theory of Bechamp and others § that the 

 formation of diastase in the higher plants, whether in germination 

 or in other metastatic processes, is due to the presence of bacteria in 

 the interior of the tissues. Besides the ordinary appliances for 

 sterilizing the vessels and instruments employed, M. Laurent placed 

 living parts of plants in a suitable nutrient substratum, after freeing 

 them entirely from bacteria, and preventing, as far as possible, infec- 

 tion through the air. The substrata employed were Koch's nutrient 



* Oomptes Eendus, ci. (1885) pp. 24-30. Cf. this Journal, ante, p. 105. 

 t Ber. Deutsch, Bot. Gesell., iii. (1885) pp. 280-9, 

 X Bull. Acad. R. Sci. Belgique, x. (1885) pp. 38-57. 

 § See this Journal, v. (1885) p. 693. 



