BROWN: WoOoDs FOR MICROSCOPIC STUDY 187 
ence to the direction of motion, such as 4°. Thin sections such 
as these require great care in handling. In most cases, particularly 
in the longitudinal planes, only extremely small pieces may be cut, 
since such sections, being less than the diameter of the cells, 
are often sections of single cells and may even be too small to be 
seen without a lens. 
After washing the sections in water to remove all glycerine, 
the celloidin may be removed by covering the sections for several 
hours with the ether-alcohol mixture. The process of clearing 
may go on very slowly and more than twenty-four hours may be 
required to remove all celloidin. The sections should now be 
placed on a slide in dilute albumen fixative (one drop to 2 c.c. 
of distilled water) and warmed slightly until dry. After standing 
over night, they are ready for staining. For staining, Koplin 
jars are best used, but otherwise the procedure is the same as for 
unimbedded material to be described in connection with differen- 
‘ tial stains. 
F, FREE HAND SECTIONS 
Since small unstained radial and tangential sections mounted 
in glycerine ordinarily show the essential anatomical features, the 
following method, though especially adapted to coniferous woods, 
is suggested, in connection with macerated preparations, to assist 
in the rapid identification of material. The radial and tangential 
surfaces are first cut true with a knife, then a sharp razor is drawn 
lightly over the surface allowing it to cut thin fragmentary pieces. 
These are placed in a drop of water on a slide and held over a 
flame until boiling temperature is reached. Alcohol is now 
dropped upon the section until all air has disappeared from the 
cell-lumina. After a brief staining in aqueous potassium iodide 
solution of iodine, the sections are ready to mount in glycerine. 
4. PREPARATION OF MATERIAL BY MACERATION 
Many tropical woods contain substances in the ray cells and 
in other elements, by reason of which details of pitting and similar 
features are obscured. Macerations will be found satisfactory 
in such instances and the following modification of Schultze’s 
method is suggested for their preparation :— 
