86 PROCEEDINGS OF SECTION B. 



The overlapping of these coustituents in the Idnos of the con- 

 necting species is shown also with their tannins, as well as with the 

 glucoside, and there is thus no sharp line of demarcation separating 

 the kinos of connecting species, and the reactions show them largely 

 to run one into the other. The Hnos thus agree, in this direction, with 

 the oils, and this overlapping of constituents appears to be the 

 natural consequence of the evolutionary nature of the genus. 



Considerable differences in chemical behaviour can, however, 

 be shown with the kinos of certain species, and in these the constituents, 

 which are representative of the class to which they belong, are present 

 in a maximum amount. The course of ascent or descent through the 

 genus may thus be roughly traced. 



No doubt, v/hen researches in other directions shall be under- 

 taken, the causes which have governed the botanical and chemical 

 alterations in the genus will be better understood. 



The following reagents have been found to be the best for the 

 purpose of readily discriminating between the members of the several 

 classes into which it has been considered advisable to arrange them : — 

 (1) Ferric chloride ; (2) Bromine water ; (3) Iodine in potas- 

 sium iodide ; (4) Potassium dichromate ; (5) Calcium 

 hydrate ; (6) Cupric sulphate and ammonia in excess ; 

 (7) Uranium acetate ; (8) Zinc acetate. 



With No. 3 iodine 5 grams and KI 12 grams in 200 c.c. water; Nos. 

 4 and 6 = 20 grams in 250 c.c. water ; Nos. 7 and 8*= 10 grams in 250 c.c. 

 Of the two last, No, 7 appears to be the better, and may be used in 

 preference to No. 8. Lead acetate has no discriminative value. The 

 strength of the kino solutions found to be best suited for the purpose 

 was 1 gram per Hfcre, except with the ferric salt test, when it was ^ 

 gram per litre. 



The best way to observe the reaction with a fairly strong solution 

 of ferric chloride is to allow one drop of the reagent to fall into the 

 solution contained in a fuU test tube, standing before a window, and 

 without agitation. It is necessary with most of the reagents to allow 

 some time to elapse, especially with the intermediate kinos, before 

 determining the results. 



The astringency or oxidizing value was determined by titration 

 with potassium permanganate, in comparison with that given by 

 gallo-tannic acid, and was found to be a most useful auxiliary test. 

 The kinos were dissolved in warm water if necessary, and the deter- 

 minations carried out in the following manner : — Solution of picked 

 kino, 1 gram per litre ; gallo-tannic acid, 1 gram per litre ; potassium 

 permanganate, 1 gram per litre ; indigotin, 5 grams and sulphuric 

 acid, 50 grams per litre, filtering through paper ; standard colour 

 solution made to match the colour of 20 c.c. of the oxidized indigotin 

 lU I litre of water, when this was just changing from green to yellow. 



