HEMICELLULOSES — ^HESPERIDIN 349 



tact with the section a slow swelling of the gum will begin, which 

 may be followed very accurately through the microscope. For 

 directions for staining see under Mucilage, and for making per- 

 manent preparations of sections containing mucilages and gums 

 see under Boracic Acid in the last chapter. 



Hemicelluloses.' — These are carbohydrate reserve materials 

 which are deposited as additions to the cell-walls in the endo- 

 sperm of seeds and in wood parenchyma and wood-fibers. By 

 means of enzymes they may be converted into gums and sugars, 

 in which forms they may be transported to those parts where 

 growth is taking place. The hemicellulose or reserve cellulose 

 in the endosperm of the date seed acts like ordinary cellulose in 

 being colored blue by chloroiodide of zinc and in dissolving in 

 cuprammonia. The reserve cellulose in the endosperm of the 

 seeds of Lupinus luteus is not dissolved in cuprammonia, and 

 does not assume a blue color when treated with chloroiodide of 

 zinc. 



Hesperidin, C21H26O12. — This glucoside occurs dissolved 

 in the cell-sap of many plants. It may be precipitated from its 

 solution in the cell-sap by means of alcohol. The precipitate 

 is in, the form of crystals, which are colorless or slightly yellow, 

 and are doubly refractive, so that they may be studied to good 

 advantage by means of the polarizer. Hesperidin is also pre- 

 cipitated on the drying up of the cell-sap. The crystals of hes- 

 peridin are insoluble in cold and boiling water, alcohol, ether, 

 benzine and dilute acids, but they are soluble in solutions of 

 caustic potash and soda, and in ammonia, yielding a yellow- 

 ish color to the solvent. Hesperidin may readily be obtained 

 for study in the unripe fruit of the orange and in the epidermal 

 cells of Capsella bursa-pastoris. Hesperiden may become de- 

 posited in the form of sphaerocrystals, when the tissues contain- 

 ing it have lain for some time in strong alcohol or glycerine, 

 acting in this respect similarly to inulin. The constituent acicu- 

 lar crystals of the hesperidin sphaerites can be more easily dis- 

 tinguished than those of inulin, and when the hesperidin sphae- 

 rites are treated with- a drop of a-naphtol, and then with two or 



