ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 921 



Easily Oxidizable Substances in Plant Sap.* — K. Ea-aus describes 

 experiments made on the sap contained in the tubers of Dahlia 

 variabilis, which he cut into slices. The surfaces gradually became 

 yellow, and with longer time the colour penetrated below the surface ; 

 the bulbs swelled, turning green in the light, and pale green chloro- 

 phyll-bodies ajipeared. The yellow tinged cells contained a yellow 

 or reddish saji ; the surfaces of the slices were not only yellow but 

 showed red points and streaks, whilst in the interior of the cells there 

 was a red colouring matter turned green by alkalies. The author 

 thinks the change of colour is due to oxidation. 



Action of Nitrous Oxide on Vegetation.f — H. MoUer claims to 

 have determined, as the result of a series of experiments, that nitrous 

 oxide has no directly injui'ious influence on living plants. 



Silicification of Organs, t — S. Miliarakis has examined the 

 silicified hairs of Deutzia scahra, Loasa vulcanica, and a number of 

 other plants, chiefly belonging to the Urticaceee, with the view of 

 ascertaining whether growth continues after the silicification has 

 taken place, which question he answers in the negative. The 

 cystoliths of Ficus and Urtica he finds to be usually surrounded by a 

 siliceous envelope ; and in F. Sycomorus, besides the ordinary cysto- 

 liths, are others completely silicified. 



Influence of Solar Rays on the Temperature of Trees.§ — 

 E. Ihne inserted thermometers at different depths into the trunk of a 

 maple tree, also in a branch and twig. He found that on a fine clear 

 day the variations of temperature were not large, the exterior layers 

 were higher than the interior, and the sections of larger diameter 

 were the warmer ; but on the whole the variations were slight, and 

 the temperature at all times of observation a considerable number of 

 degrees above that of the surrounding atmosphere. 



Thermic Constants in Plants. || — The thermal constant of a plant, 

 according to Oettinger, is the sum of the mean temperatures of the 

 days of active vegetation from the commencement of growth to some 

 definite phase in the plant's life, minus a certain initial temperature, 

 different for different species, and determined by comparing the 

 observations of successive years. Staub objects to this, that the 

 development of a plant dej)ends not only on the aggregate quantity 

 of heat which it receives, but above all on the temperature during 

 growth, which cannot be expressed by adding together thermometric 

 measurements. 



* Bied. Centr., 1884, pp. 45-G. See Journ. Cham. Soc— Abstr., xlvi. (1884) 

 p. 918. Cf. this Journal, ante, p. 255. 



t Ber. Deutsch. Bot. Gosell., ii. (1884) pp. 35-41. 



X Miliarakis, S., 'Die Verkieselung lebendor Elementar-organe bci den 

 Pflaiizen,' 30 pp., Wurzburg, 1884. Sec Bot. Centralbl., xviii. (1884) p. 23.'). 



§ Bied. Gcntr., 1»84, p. G3. See Jouru. Cliem. Soc— Abstr., xlvi. (1884) 

 p. 917. 



II Botan. .Tahreeber., iii. (1884) p. 131. See Journ. Cbem. Soc.— Abstr, xlvi. 

 (1884) p. 10G7. 



Ser. 2.— Vol. IV. 3 p 



