58 BOTANICAL GAZETTE [JANUARY 
3. DEMINERALIZATION.—It will be found advantagous to use much 
stronger solutions of hydrofluoric acid with the harder woods. The 
material should be allowed to remain about two weeks in a solution of one 
part commercial acid to one part water. In the case of very hard woods, 
such as live oak, ebony, eucalyptus, etc., pure acid may be used to advantage 
and the wood soaked two to three weeks. The percentage of solution and 
length of immersion depend on the hardness of the wood, and should be — 
varied to meet the demands of each species. The acid should be thoroughly 
washed out, and the material left for several days in a mixture of one part _ 
30 per cent. alcohol to one part glycerin. ; 
4. SECTIONING.—This part of the process requires considerable skill 
and experience, besides the use of the best microtomes and knives. The 
Jung sliding microtome for wood sectioning is the best, but needs much 
heavier and more solid carriers. The carriers should have long antifriction- 
metal bearings and some device similar to that provided with the celloidin 
microtome for adjusting the object carrier to the desired plane of section. 
The success of working the microtome depends upon keeping the knife 
absolutely free from nicks and extremely sharp, in having all the bearings 
free from dust and dirt and well oiled, in regulating the angle at which the 
knife cuts, and in orienting the surface of the block in accordance with 
the hardness and structure of the wood. 
5. USE OF CELLOIDIN.—The celloidin method is unnecessary in cutting 
thin sections of woody tissues except in the case of small fragments. Even 
the latter may often be cut successfully without imbedding by gluing to 
the carrier block with a few coats of 4 per cent. celloidin. In working with 
extremely soft woods, decayed woods, or in making careful studies of 
soft structures like the resin canals of the white pines, the celloidin method 
is useful. 
6. CUTTING WITHOUT DEMINERALIZATION.—Sections of soft woods as 
thin as 5 # may be cut after boiling without demineralization, but for this 
purpose an old knife which can be repeatedly honed and sharpened is 
needed. 
7. STAINING.—For most purposes the hematoxylin-safranin double 
stain is the most serviceable; but in studying special structures, such 4s 
spiral markings and the pitting of conifers, unstained sections mounted 
in glycerin jelly are preferable. In fact, in any given problem experiment 
with the various steps of the method is necessary to secure the best results. 
When the structures are obscured by deposits of resinous materials, tannins, 
etc., these must often be removed to reveal the pitting and sculpture of 
the cell walls.—Irvine W. Baitey, Harvard University. 
