421 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and cJiloroamylites, witli a ternary skeleton, originating from starch-grains. 

 In the latter case the protoplasm of the cell takes no part in the production 

 of the chlorophyll-grains. Starch is, however, necessary for the formation 

 of the skeleton of both chloroleucites and chloroamylites, and for the 

 development of the chlorophyll-pigment. When starch is wanting, chloro- 

 amylites lose their green colour and finally disappear; they are usually 

 of a temporary character, while chloroleucites may remain dixring the whole 

 life of the plant. 



Composition of the Starch-grain.* — M. E. Bourquelot has made a 

 number of observations on the chemical constitution of starch-grains, 'which 

 result in the view that they are not composed of only one or two chemical 

 bodies (granulose and amylose), as has been hitherto supposed, but of a 

 larger number of carbohydrates. 



Starch-grains coloured red by iodine. — Hcrr A. Meyer finds, j in 

 seventeen different species of plant belonging to seven different families, 

 starch-grains which take a red colour with iodine. In Goodijera discolor 

 they are compound. They were examined chiefly in the endosperm of 

 Chinese and Japanese species of Sorghum. They do not differ in appearance 

 from those which are coloured blue, but are much more readily broken 

 up ; they take a rather higher temperature to make them swell ; and 

 the black cross is more conspicuous with polarized light ; they are more 

 rapidly acted on by ferments. After treatment with acids they show a 

 distinct lamination, and are coloured only a very faint red by iodine. From 

 their various reactions, Meyer believes that the difference between these 

 grains and those that are stained blue by iodine is that, in addition to 

 " starch-substance," J they contain amylodextrin, and a third substance 

 which is not coloured by iodine, and is soluble in w^ater, probably a 

 dextrin. Those grains which take a violet colour with iodine contain traces 

 of amylodextrin, and perhaps also of dextrin ; those which are coloured 

 red, only a small quantity of starch-substance. He believes them to be 

 formed, by a kind of fermentation, from the " blue " grains. 



Herr F. W. Dafert § contests several of the points insisted on by Meyer 

 in this paper, and maintains, among others, that amylodextrin does not 

 occur in potato-starch. 



Soluble Starch. II — Herr J. Kraus, having found, dissolved in the cell- 

 sap of the epidermis of some Arums, a substance previously met with by 

 Dufour and others in the epidermis of Ornithogalum and Gagea, has come 

 to the conclusion that it is allied to the tannins. It gives a blue colour 

 with iodine, chloriodide of zinc colours it rose, ferric chloride and ferrous 

 sulphate give a brownish-green ; on the other hand, potassium dichromate 

 and Gardiner's reagent give no reactions. The substance behaves like a 

 tannin in being developed under the influence of liglit, and in persisting 

 without alteration in dead or dying leaves. That iodine should give a blue 

 colour with tannin is not surprising, since Giessmayer has shown that a 

 solution of tannin gives with a weak solution of iodine, in feebly alkaline 

 water, a bright red colour, and, under certain conditions, according to 

 Nasser, a red -purple. 



* Comptes Rendus, civ. (1887) pp. 177-80. 



t Ber. Deutsch. Bot. Gebell., iv. (188G) pp. 337-G2 (1 pi. and 1 fig.). 

 X See this Journal, ante, p. 256. 

 § Ber. Deutsch. Bot. Gesell., v. (1887) pp. 108-14. 



II Ann. Agronom., xii. (1886) pp. 540-1. See Journ. Chem. Soc. Lend., 1887, Abstr,, 

 p. 173. Cf. this Journal, 1886, p. 819. 



