778 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The most abundant acid in the sap is malic, occurring either free 

 or as calcium malate; the amount of this salt appears to remain 

 nearly constant by day and by night. 



Kraus regards the vegetable acids as secondary products of 

 respiration, occurring especially in those parts which contain abund- 

 ance of protoplasm, the medium of respiration. He does not support 

 the view that they are products of assimilation. 



New Colouring Substance from Chlorophyll.* — E. Sachsse dis- 

 tinguishes two varieties of the derivative from chlorophyll previously 

 described by him as phyllocyanin, but which he now prefers to call 

 phfeochlorophyll, viz. : — a pheeochlorophyll, almost insoluble, and 

 /3 phseochlorophyll, soluble with difficulty in alcohol. The latter 

 substance is, when dry, nearly black, insoluble in water, soluble in 

 alcohol, from which it separates on cooling in amorphous flakes, 

 and in benzol. It is distinguished by its peculiar brown-yellow- 

 green colour, and its formula is C27H33N3O4. 



By heating (B phfeochlorophyll with baryta water or fusing with 

 soda, it is deprived of carbonic acid, and a new substance obtained 

 with the composition C26H33N3O2, which, when dry, is of a dark red- 

 brown colour. Its solution in alcohol is dark red, which a few 

 drops of sulphuric acid change to light red-violet. The colour itself 

 and the spectrum are very similar to those of an alcoholic extract of 

 violets. Saturation of an acid solution with alkali gives, however, 

 a yellow or, in very concentrated solution, a red colour instead of 

 green. Dry distillation with soda gives a crystalline sublimate 

 soluble in alcohol and extremely soluble in ether. 



Crystalline Chlorophyll.! — J. Borodin believes that he has 

 obtained the long-desired result of pure chlorophyll in a crystalline 

 form by slow evaporation of an alcoholic solution, though he has not 

 as yet been able to isolate the crystals. They are doubly refractive, 

 giving a beautiful green sheen in polarized light. Their physical 

 properties differ from those of the dark-green crystals of hypochlorin 

 hitherto obtained. 



Crystals and Crystallites. J — By the term crystallites A. 

 Famintzin designates structures which agree neither with crystals 

 nor with the organized products of living cells. They may be 

 arranged under four different types, connected by transitional forms. 



The mode of formation of crystals was illustrated by artificial 

 crystals of potassium phosphate and magnesium sulphate. From 

 these the author established the following points : (1) The original 

 form of the crystal is not always its permanent form. (2) Crystals 

 are formed constituting the half or even the fourth of a double 

 rhombic pyramid. (3) Crystals do not always grow with flat surfaces, 



* SB. Naturf. Gesell. Leipzig, x. (1883) pp. 97-101. 



t SB. Vers. Buss. Naturf. u. Aerzte, Odessa, Aug. 25, 1883, See Bot. 

 Centralbl., xviii. (1884) p. 188. 



J SB. Vers. Buss. Naturf. u. Aerzte, Odessa, Aug. 24, 1883. See Bot. 

 Centralbl., xviii. (1884) p. 158. 



