98 ELEMENTS OF APPLIED MICROSCOPY. 
ity of the cells are straight or bent or curled, markings, 
size and character of the central canal, if'any. Polarized 
light is often of great service in the identification of paper 
fibres. 
4. Analytical Key to Paper Fibres.—The authors 
above mentioned suggest the following useful key for 
the preliminary examination of paper. In this table 
the word fibre is restricted to those cells which are very 
long in proportion to their breadth. 
ANALYTICAL SCHEME. 
A. Fibres are characteristic; other characteristic forms absent. 
I. Fibres are Jong; greater than diameter of field (Mag. =60). 
(1) Fibre has many joints, knots, or projections, especially 
by polarized light. 
(a) Fibre is fine; quite smooth; joints not very notice- 
"able. 
Paper mulberry— Manila hemp— Agave. 
(®) Fibre is coarse; uneven; joints are large and promi- 
nent. : 
Linen—Jute—Hemp (Cannabis sativa). 
(c) Fibre shows overlapping scales. 
Wool. 
(2) Fibre has peculiar markings; dotted, circular, square, 
"— net-like. 
(a) Markings resemble circular or square perforations. 
Spruce (fir, hemlock, tamarack, balsam)—Pine— 
Redwood—Red cedar— Arbor vite—Cypress. 
(0) Markings net-like, ‘‘feather-stitch,” spiral. 
Redwood — Cypress — Banana  (jruit- stem) — 
Ramie. 
-- (3) Fibre is smooth and regular. 
(a) Many fibres resemble twisted ribbons. 
Cotton—Banana (stalk and leaj-stem). 
(b) Fibres are round, cylindrical. 
Sik—Sisal hemp—Bark of cotton-stalk. 
