34 American Quarterly Microscopical Journal. 



In strong cold sulphuric acid, silk quickly turns yellow and 

 dissolves, cotton disintegrates slowly without color, flax and 

 hemp make a black mixture, and wool is scarcely affected. 



Both silk and wool turn yellow and are soluble in nitric acid, 

 the first the more speedily, while vegetable fibers are slightly 

 affected. For these, cupro-ammonium sulphate is considered 

 the only solvent. 



When treated with iodine and dilute sulphuric acid, vegeta- 

 ble fibers, composed chiefly of cellulose, take a characteristic 

 color, either yellow or blue, while animal fibers are not affected. 

 These reagents, applied under the microscope, afford the means, 

 in connection with the characters of the ultimate cells of which 

 all plant fibers are composed, of determining the species from 

 which the fiber is derived. The reagents should be prepared 

 as follows : — Dissolve one part potassium iodide in one hundred 

 parts of distilled water, and add an excess of pure iodine so 

 that the solution shall always remain saturated. Mix one part of 

 distilled water with three parts of sulphuric acid, and when cool 

 add two parts of Price's glycerin. Both reagents should be kept 

 in glass stoppered bottles, and as they are liable to change, 

 should be occasionally tested on known fibers. When in proper 

 condition they will give clear and uniform coloration without 

 changing in the slightest degree the form of the fiber cells. If 

 the acid be too strong the fiber takes an intense color, and 

 swells enormously, often in a very symmetrical manner as fig- 

 ured in Sach's Botany, English Ed., page 592, etc., but this 

 tumefaction should be carefully avoided in differentiating fibers. 

 The simplest form of vegetable fiber consists of appendages to 

 seeds like cotton; single cells almost without taper, but usually 

 they are composed of bundles of tapering or spindle shaped 

 tough, firm cells, lying side by side, and separable from each 

 other by soaking in alkalies, rubbing with the fingers, teasing 

 with needles, rubbing with a pestle, or recourse must sometimes 

 be had to boiling in ten per cent, soda lye or Labarraque 

 solution. 



When the cells are separated a number of them should be 

 extended on a slip and slightly moistened with glycerin, which 

 will restrain any tendency to crisp or curl when the cover is 

 imposed. By laying the slip on a rule the average length is 

 determined, then a micrometer must be used for the diameter. 

 Now observe the ends for shape, taper, and whether or no 



