ZOOLOGY AND BOTANY, MICROSCOPY^ ETC. 257 



absorption-bands of tbis substance, and of tbe colouring matter of 

 Anchusa tindoria, alkanet red, the spectrum of eacb showing three 

 bands occupying identical positions. These investigations have there- 

 fore so far afforded proof of the existence in the colourless cells of 

 the sugar-beet of an easily oxidizable colourless body, capable of iso- 

 lation, which by itself, without the aid of the living protoplasm of 

 the plant, can split up the oxygen molecule, forming a coloured 

 substance. 



The isolation of the chromogen of the potato has not succeeded so 

 satisfactorily. The presence of vanillin in the juice appeared to be 

 shown by the strong odour of vanilla. Vanillin has been detected 

 by Scheibler in raw beet-sugar. A substance resembling catechol, 

 but not identical with it, was also separated. It would seem to be 

 the same body discovered by Gorup-Desanez in the leaves of the 

 Virginian creeper. It is undoubtedly an acid, and, amongst the known 

 aromatic acids, most closely corresponds in its reactions with hydro- 

 caffeic acid. In conclusion, the author suggests the hypothesis that 

 these easily oxidizable bodies belong, in their physiological relations, 

 to the retrogressive series, perhaps originating from the breaking up 

 of albumin, or formed by the synthesis of the products of such decom- 

 position, and that in these features the process is allied to that of 

 respiration. 



Action of Light on the Elimination of Oxygen.* — The following 

 are the main results of a series of experiments by J. Keinke on 

 Elodea : — 



The evolution of oxygen which is dependent on light begins with a 

 mean illumination and increases pari passu to a maximum with 

 increasing intensity of light, this optimum corresponding nearly 

 to direct sunlight ; any further increase in the intensity of light does 

 not increase the development of gas. Indicating the intensity of 

 ordinary direct sunlight by 1, one-fourth that amount by 1/4, and four 

 times that amoimt by 4/1, the two lower rows in the following table 

 indicate the number of bubbles given off in 1/4 minute in two 

 different experiments : — 



1/1 4/1 16/1 36/1 64/1 



30 32 31 26 27 



28 31 28 30 29 



In light of 800/1, the plant gave off in two minutes the same 

 number of babbles as in ordinary sunlight ; the stream then ceased, 

 the chlorophyll being bleached. In light of from 64/1 to 300/1 

 intensity, the gases exhaled do not contain more carbonic acid than 

 that produced by the green plant in ordinary sunlight. From all 

 these facts he draws a conclusion unfavourable to Pringsheim's 

 hypothesis that chlorophyll acts as a protecting screen against the light. 



Red Pigment of Flowering Plants.t — H. Pick points out that 

 those organs of flowering plants in which carbo-hydrates are present 



* Bot. Ztg., xli. (1883) pp. 697-707, 713-23, 732-8. 



t Bot. Centralbl., xvi, (1883) pp. 281-4, 3M-S, 3-13-7, 375-83 (1 pi.). 



