A microchemical test for cellulose applicable to fresh sections and commercial products is described. The test differs from the older technics in that materials tested are not permanently altered. Two solutions are required: (1) 2% solution of iodine in 5% KI, diluted with 9 parts by volume of water containing 0.28% glycerin; (2) saturated aqueous LiCl. Procedure: Apply 2 or 3 drops of solution 1 with a glass rod; allow the preparation to stand for 30 sec; blot with filter paper, drying as completely as possible. Apply one drop of solution 2, cover and examine. The color reaction will be obtained within 5 min. The reaction for pure cellulose is light blue. Reactions for 16 fibers are given in the table. As a stain for demonstrating plant tissues the technic has been used in the Botany Department of Pomona College with much success; but this phase of the subject has not been extensively investigated.