356 USEFUL FIBER PLANTS OF THE WORLD. 



After finding the length, sections of the fibers must be made to deter- 

 mine the diameter of the cells. For this purpose the writer has some- 

 times rolled a little bundle of the fibers in a piece of sheet wax made 

 warm enough to be pliable. The wax is allowed to cool, and the sec- 

 tions cut in any section cutter, of which there are now a great many 

 forms in use by microscopists. If the fibers are hard, the wax is not 

 sufficiently resistant, and an embedding mass must be used that may 

 be prepared by dissolving 70 grams of clean gum arabic in an equal 

 weight of distilled water. Then digest 4 grams isinglass in 16 grams 

 cold water till swollen, then heat to complete solution. 



Strain one-half through a piece of fine muslin and mix with the solu- 

 tion of gum arabic, throwing the rest away, and add 10 or 12 cubic 

 centimeters of glycerol, warm and mix thoroughly, and in each bottle 

 put a small piece of camphor. It is best to put it up in small bottles, 

 as it solidifies on cooliug. When it is to be used, warm the bottle, and 

 taking a little bundle of the fibers, about the size of a slate pencil, tie 

 a thread around one end and saturating the bundle with the glue, 

 stroke the fibers till they are straight and parallel, then hang the bun- 

 dle up to dry for about twelve hours, when it will be hard enough to 

 cut. The slices are placed on the slide, and wet with iodin solution, 

 which is in turn absorbed by strips of blotting paper till all the glue is 

 dissolved and removed. When the sections are made in wax, benzine 

 or turpentine may be used for this removal, and the iodin applied sub- 

 sequently. When the sections are clean, a drop of the dilute sulphuric 

 acid is put on them, the cover glass is placed in position, and they are 

 ready for examination on the stage of the microscope. Or the cover 

 glass may be put on before the addition of the sulphuric acid, and the 

 acid then placed on the slide at the edge of the cover glass, when it 

 will slowly creep under, and its progressive action can be watched as 

 it penetrates the sections. Pure cellulose takes a blue color, lignin a 

 yellow, and intermediate tints will be produced in proportion as the 

 cells are more or less lignified. When the saturation is complete, the 

 outline of the sections will be sharply made out, and their diameter, 

 shape of outline, and character of the interior canal should be noted. 

 As the relative proportion of lignin and cellulose differs much in the 

 cells of different plants, but is tolerably constant for the same species, 

 it is possible to classify fibers according to their reactions, which taken 

 in connection with the size of their ultimate fiber cells, offer us the 

 most certain means of identification, and these characters will be found 

 synoptically arranged in the table following. By a careful use of strips 

 of blotting paper to take up any excess of reagents, all injury to the 

 microscope may be avoided and much better results obtained than by a 

 sloppy, careless method of work. For measuring the diameter of the 

 cells a Jackson eyepiece micrometer is to be preferred. The gross 

 appearance of the fibers should be noted in most cases. If the ends 

 are frayed and worn it indicates shoddy in wool and paper stock in 

 •otton. In the United States, where much paper stock is of wood, 



