116 
METHODS IN PLANT HISTOLOGY 
With the generic name written on the box, it is easy to find anything 
in the large collection. 
CUTTING 
As soon as the paraffin is thoroughly cooled, it is ready for cutting. 
Trim the paraffin containing the object into a convenient shape, and 
fasten it upon a block of wood. Blocks of pine f inch long and f inch 
square are good for general purposes. Put paraffin on the end of the 
block so as to form a firm cap about J inch thick. Warm the cap 
and the bottom of the piece containing the object, and press them 
lightly together; then touch the joint with a hot needle, put the 
whole thing into cold water for a minute, and it is ready for cutting. 
Cutting can be learned only by experience, but a few hints may not 
come amiss: 
a) Keep the knife sharp. There should be two hones, one for 
use when the knife is- rather dull and the other for finishing. For 
the first hone, nothing equals a fine carborundum hone. About 
5.5X22.5 cm. is a good size. A hard Belgian hone, of the same 
size, may be a little better for finishing. Flood the stone with water, 
and rub it with the small slip which accompanies all high-grade hones; 
this not only makes a lather which facilitates the sharpening, but 
it also keeps the surface of the hone flat. As soon as the edge of the 
knife appears smooth and even under a magnification of 30 or 40 
diameters, the sharpening is completed with a good strop. It is 
better to sharpen the knife every time you use it. A first-class 
microtome knife, in perfect condition, is unsurpassed for cutting 
paraffin sections, but it requires both time and skill to keep the edge 
perfect. More than 20 years ago we began to experiment with the 
Gillette safety-razor blade and devised several holders for it, some 
of them more or less successful. Mr. Strickler finally perfected a 
holder which has already been mentioned. In using this holder 
the blade should not project more than 1 mm. The Gillette blade is 
harder than the ordinary microtome knife, and is so sharp that the 
edge appears smooth, even under a high-power dry lens. The bevel 
is about the same as that of a microtome knife which has been 
“backed” for sharpening. With this blade in the holder as made 
by Mr. Strickler or Mr. Larsen, we have cut smooth ribbons of 
Selaginella strobili, sections through the sporangium region of the 
whole plant of Isoetes, sections of stems of Cucurbita, in fact, we have 
not used an ordinary microtome knife for cutting paraffin ribbons for 
