568 ELEMENTS OF PLANT HISTOLOGY AND MICEOTECHNIC 



tion of potassium hydrate, long columnar or needle-shaped crystals of potassium 

 caryophyllate are produced. When sections of cloves are used, they often become 

 covered by the forming crystals. 



Fats and Fatty Oils. These are insoluble in cold and hot water, and, with the 

 exception of castor oil, hardly soluble in alcohol, but readily soluble in ether, chloro- 

 form, benzol, ethereal oils, acetone, and wood spirit. They make a spot on paper 

 which does not disappear, as in the case of ethereal oils. Most fats and fatty oils 

 are colored brown or black by I per cent, osmic acid. When a drop of fat or fatty 

 oil is placed on a glass slide in a drop of a mixture of equal parts of concentrated 

 potassium hydrate and ammonium, the oil becomes saponified, and may assume a 

 form like a bunch of grapes, or it may be partly or wholly changed into clusters 

 of soap crystals. Vapor of hydrochloric acid has been used to distinguish between 

 ethereal and fatty oils. A large and a small glass ring, such as are used for hanging- 

 drop cultures, are cemented to a glass slide, the small one being shallower than 

 the large one, and placed within it concentrically. Hydrochloric acid is placed 

 into the space between the rings, and the sections to be tested are placed on a 

 cover-glass in a drop of glycerine containing a large amount of sugar. 



The cover-glass is then inverted and placed on the larger ring. After the vapor 

 of hydrochloric acid has had time to act, any ethereal oil present in the sections will 

 take on the form of bright yellow drops which finally disappear. Fatty oils do not 

 form yellow drops by this treatment. A solution of alcannin colors the fats red, 

 but several hours may be required to accomplish this. A solution of cyanin in 50 

 per cent, alcohol is also a good stain for fats. The sections will not need to lie in 

 this stain longer than half an hour. If sections are overstained, they may be 

 washed out in glycerine or a concentrated solution of potassium hydrate. 



Frangulin, CzoH^oOio. This glucoside occurs in the cortex of species of Rham- 

 nus. It forms yellow crystalline masses which are insoluble in water, but soluble 

 in alkalies, which produce with it a cherry-red color. Concentrated sulphuric 

 acid produces with frangulin an emerald-green, which changes into purple, and 

 finally the frangulin dissolves with a" dark red color. Water will precipitate it from 

 this solution. 



Fungus Cellulose. The membranes of very few fungi give the reactions of 

 cellulose. The membranes of most fungi are insoluble in cuprammonia, and are 

 colored from yellow to brown by chloroiodide of zinc, sulphuric acid and iodine. 

 Neither do they react in the same manner as suberized and lignified membranes. 

 They are, therefore, considered to be a distinct substance, which is termed fungus 

 cellulose. See also under Chitin. 



Gelatinous Sheaths. The homogeneous gelatinous sheaths which cover the 

 entire outside of certain algae notably, species of Spirogyra and Zygnema may 

 be demonstrated by the use of certain stains and other substances, such as India 

 ink, which may become deposited in the sheaths. Aqueous solutions of vesuvin, 

 methyl- violet, and methylene-blue will stain both the cell- walls and gelatinous 

 sheaths, but the latter with less intensity. Chloroiodide of zinc will stain the walls 

 without affecting the sheaths; Turnbull's blue may be deposited in the gelatinous 

 sheaths in the following manner: A small number of zygnema filaments, for in- 

 stance, may be tied together with a thread and placed for about 2 minutes in a 2 

 per cent, solution of ferrous lactate, then quickly washed in water, and transferred 

 to a 0.2 per cent, solution of ferricyanide of potassium. A small amount of Turn- 

 bull's blue will then be deposited in the gelatinous sheaths. This process should 

 be repeated several times, until the deposit of Turnbull's blue is sufficiently dense 

 to cause the sheaths to stand out quite sharply. By this method very instructive 



