606 SUMMARY OF CURRENT RESEARCHES RELATING TO 



find a large vacuole with coloured contents and a number of small ones 

 with uncoloured cell-sap. This is the case, for example, in the petals of 

 Camellia japonica. From this fact a conclusion is drawn favourable to the 

 view that the wall of the vacuole .takes an active part in the storing up of 

 the substances dissolved in the cell-sap. 



(2) Other Cell-contents. 



Acidity of the Cell-sap.* — Dr. Lauge has investigated the nature 

 and proportion of the acid constituents of the cell-sap in a number of 

 plants, both succulent and thin-leaved. He supports Warburg's statement f 

 that the less refrangible rays of the spectrum are more efficacious in decom- 

 posing acids than the violet portion. Although dead plants contain a 

 smaller proportion of acids than living plants, this is not, he states, due to 

 the presence of carbonic acid in the living plant. The author confirms 

 the observation of Kjraus, of a periodical increase in the acidity of the sap 

 in the morning and a corresponding decrease in the evening. As a general 

 rule, chemical changes in the plant proceed much more energetically in 

 the luminous or red than in the chemical or blue half of the spectrum. 

 Tables are appended of the amount of acid found in the cell-sap of a number 

 of plants at different periods of the day. 



Chemistry of Chlorophyll, f — Mr. E. Schunk, considering the intimate 

 connection between chlorophyll and the carbon dioxide of the atmosphere, 

 thought it might be interesting to ascertain whether compounds of phyllo- 

 cyanin could be obtained in which the organic or other acid could be re- 

 placed by carbonic acid. On passing a current of carbonic acid for several 

 hours through an alcoholic solution of phyllocyanin holding hydrated zinc 

 oxide in suspension, and by further agencies, a compound is obtained which 

 is a phyllocyanin zinc carbonate; this is decomposed by the action of 

 strong acids, and yields phyllocyanin and carbonic acid. The author gives 

 an account of the action of caustic alkali and zinc, and of hydrochloric acid 

 and metallic tin on phyllocyanin. 



Researches on Chlorophyll.§ — Herr A. Tschirch gives a resume of the 

 most recent observations on the composition of chlorophyll, and confirms 

 his previous view that iron is not a necessary constituent of the green 

 colouring matter of leaves. 



For phyllocyanic acid (Schunck's phyllocyanin) he gives the formula 



As regards the proportion in leaves of the substance to which the 

 absorption of CO2 is due, he finds in Fuchsia ovata that it constitutes from 

 2*55 to 4-71 per cent, of the dried substance freed from ash, and from 

 0*6081 to 1*0 g. per sq. m. of the surface of the leaf. In Begonia 

 manicata the figures were 1 • 8 per cent, and • 3808 g. per sq. m. ; in 

 Plectogyne sp. 1*92 per cent, and 1-2328 g. per sq. m. 



Researches on Green and Yellow Chlorophyll. || — Dr. A. Hansen states 

 that the orange-red pigment stated by several observers to have been found 

 in leaves along with the yellow and red, is simply aggregations of the 

 yellow chlorophyll-pigment, which has an orange tint when present in 

 dense masses. He even obtained orange-red crystals. 



* Ber. Naturf. Gesell. Halle, 1886, pp. 4-29. f See this Journal, 1886, p. 478. 



X Proc. Roy. See. Load., xlii. (1887) pp. 184-8 (1 pi.). 



i; Ber. Deutscli. Bot. Gesell., v. (1887) pp. 128-35. Cf. tliis Jourual, 1886, p. 88. 



il Arbeit. Bot. lust. Wiirzburg, iii. (1887) pp. 480-2. 



