PLANT PRODUCTS 567 



solution which loses its color on the addition of acetic or dilute hydrochloric acid. 

 In the presence of datiscin, acetate of lead and chloride of zinc produce a yellow, 

 oxides of copper a greenish, and chloride of iron a dark bluish-green, precipitate. 



Dextrine, Ci 2 H 2 oOio. This is one of the intermediate products between starch 

 and maltose (see Amylose). It is easily soluble in water, and from its aqueous 

 solution it may be precipitated by strong alcohol. It is not colored by iodine, and 

 does not reduce salts of copper. 



Dextrose (Glucose, Grape-sugar). See under Glucose. 



Diastase. To demonstrate the presence of diastase in sections they are laid 

 for a time in a dark brown solution of guaiacum in absolute alcohol. When the 

 sections are completely infiltrated with this solution the alcohol is allowed to 

 evaporate, and then the sections are placed in a rather dilute solution of hydrogen 

 peroxide. By this treatment cells containing diastase are colored a beautiful blue. 

 See also under Diastase Solution in the preceding chapter. 



Dulcite, CeHuOe. Dulcite may be demonstrated in sections from one-year- 

 old stems of Euonymus japonicus. The sections are placed on a slide in a few drops 

 of alcohol, and covered with a cover-glass. After the alcohol has slowly evaporated 

 from under the cover-glass, crystals of dulcite will be deposited in the form of long, 

 branched prisms or needles radiating from a common center. They are distin- 

 guished from crystals of potassium nitrate by dissolving in diphenylamine and 

 sulphuric acid without coloration, and by being insoluble in a concentrated 

 solution of dulcite. 



Elaioplasts. They are rounded or irregularly polygonal, more or less granular 

 bodies, consisting of a protoplasmic stroma and inclosed oil, which occur closely 

 applied to the nucleus in the epidermal cells of many monocotyledonous and some 

 dicotyledonous plants. In old cells the elaioplasts have the appearance of a 

 sponge saturated with oil. The oil in the elaioplast of Ornithogalum umbellatum 

 may be almost instantly dissolved by means of alcohol. These elaioplasts may 

 be fixed and stained at the same time by treating sections containing them with a 

 dilute solution of alcannin in i per cent, acetic or formic acid. The acid fixes the 

 protoplasmic stroma, while the alcannin stains the oil a beautiful red. The fixing 

 and staining process should be complete in 5 minutes. If desired, the sections 

 may be double-stained by transferring them from the alcannin to a solution of 

 iodine-green and glycerine, after which they may be mounted in glycerine- jelly. 

 The sectipns may also be stained in a mixture of a dilute solution of alcannin and 

 a solution of iodine-green in 50 per cent, alcohol and i per cent, acetic acid. 



Emulsin. This is a glucoside-splitting ferment which occurs in certain cells 

 of the almond and of the bundle-sheath of the leaves of Prunus laurocerasus. 

 When sections are treated with Millon's reagent, the cells containing emulsin take 

 on an orange-red color, while the surrounding cells are colored a pale rose-red. 

 A solution of copper sulphate and caustic potash produces a violet color in the 

 emulsin-bearing cells. 



Ethereal Oils. Ethereal oils are distinguished from fatty oils in that they may 

 be distilled from plants along with vapor of water, and are soluble in glacial acetic 

 acid, and an aqueous solution of chloral hydrate. At I3OC. all ethereal oils may 

 be driven from sections, while the fatty oils remain behind. Ethereal oils are only 

 slightly soluble in water, but they impart their smell strongly to it. They are 

 easily soluble in ether, chloroform, and fatty oils. The spot produced on paper by 

 ethereal oils soon disappears. They agree with the fatty oils in being browned or 

 blackened by osmic acid, and in being stained by alcannin and cyanin. 



Eugenol, C6Hs.OH.OCHt.CsHs. Eugenol occurs in clove and pimento oil. 

 When sections containing either of these oils are treated with a concentrated solu- 



