25 



present. By removing the twig to a bath of alcohol for a 

 minute the subject was cleared up, and the location of the 

 starch-bearing portions could be made out more distinctly. 

 If desired, thin sections could be taken from the treated sur- 

 face for microscopic study. 



Sugars. — The sucrars of various sorts are usually associated 

 with each other, and only the presence or absence of the group 

 was usually attempted. Trommer's test is a simple and satis- 

 factory one: Place the slices or sections in a porcelain dish, 

 add a strong solution of cupric sulphate and heat to boiling. 

 Wash the specimens thoroughly, and add hot potassic hydrate, 

 when the presence of dextrine and grape-sugar will be shown 

 by a reddish precipitate. To separate these two sugars, treat 

 the original tissue to alcohol, standard strength, for a few 

 hours, which will dissolve away the grape-sugar, when the 

 dextrine can be tested for as before. Cane-sugar, with Trom- 

 mer's, gives a bright blue color in the cell contents, quickly 

 vanishing, but no red precipitate. It is well for the student to 

 make tests with this reagent of vegetable tissues containing 

 large quantities of each one of the leading kinds of sugars. 

 Fehling's solution, which is a modification of the above, may 

 be employed. In place of the pure cupric sulphate solution, 

 one of one part of the cupric sulphate and five parts of potas- 

 sium sodium tartrate in eight parts of water may be used. 

 This reagent needs to be kept in the dark. 



Albuminoids. — For these Millon's reagent was employed. 

 This is prepared by adding to metallic mercury an equal 

 weight of concentrated nitric acid. VV^hen all is dissolved add 

 twice the volume of pure water. Place the tissue in a porce- 

 lain dish, add a little of the reagent and heat, when a rose or 

 brick-red precipitate indicates the presence of albuminoids. A 

 dark yellow, with nitric acid, and a yellow or brown with 

 iodine also indicate the same substances. 



Crystals. — There are two leading salts in the form of 

 crystals in plants, the carbonate of lime and the oxalate. 

 The crystals having been detected with the microscope, acetic 

 acid may be added, which will dissolve the carbonate with 

 effervescence, but does not act upon the oxalate. 



Tannin. — The various iron salts give with tannin a very 



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