94 BOTANICAL MICROTECHNIQUE. 



those of inulin by having usually a much less rounded form 

 than the latter, and by showing their com- 

 position from separate acicular crystals 

 much more clearly. The latter is the case 

 especially in the smaller sphaerites (cf. 

 Fig. 28, a and b) ; the larger ones com- 

 monly contain in the middle a more ho- 

 K: II mogeneous nucleus, as Fig. 28, c shows in 



optical median section. 



F,O. 28 .-Hes P eridin cr ys - The hesperidin crystals readily dissolve 

 tfe^uJ^ltirS'* 1 an alcoholi c or aqueous solution of 

 citrus Aurantium. caustic potash, forming a yellow fluid, but 

 are not noticeably soluble in cold or hot water or in dilute 

 acids ; while inulin is at once completely dissolved by boil- 

 ing water. 



The sphaerocrystals of hesperidin are also soluble in boil- 

 ing concentrated acetic acid, ammonia, and soda solution, but 

 are insoluble in ether, benzol, chloroform, carbon bisulphide, 

 and acetone. They are completely destroyed on heating to 

 a red heat. 



The observation and preservation of these crystals in 

 Canada balsam may be readily accomplished after clearing 

 in oil of cloves. Canada balsam preparations are especially 

 adapted to their study by polarized light, with which they 

 give the same appearance as inulin sphaerites. 



e. Coffee-tannin, C 15 H 18 O 8 . 



155. Coffee-tannin, according to Molisch (I, 9), shows the 

 following reactions, which may easily be followed under the 

 microscope on sections of the endosperm of the coffee-bean. 

 With ferric cJiloride it is colored dark green, with ammonia 

 and caustic potash deep yellow. If sections are allowed to 

 dry with a drop of ammonia, they finally take a green color, 

 which at once changes to red on moistening with concen- 

 trated sulphuric acid. An abundant precipitate is formed 

 with lead acetate. 



