APPENDIX II 687 
Sutruric Acrp.—Concentrated sulfuric acid, containing 
from 93 to 95 per cent. of H2SO, is useful in the detection of 
suberized or corky walls. These resist its action, while lignified 
and cellulose walls are completely dissolved by it. This acid as 
well as dilutions of it with water are also employed fer se or with 
various chemicals in a number of microchemic tests. 
Additional reagents and stains are discussed under appropri- 
ate headings in this and other chapters of the text. 
Tue TECHNIQUE OF Maxkinc A TEMPORARY Mount 
1. Place a drop or two of water (or reagent) in the center of a 
clean glass slide. 
2. With the aid of a forceps take the section or very small 
quantity of the material to be examined and spread it on the drop 
of water. 
3. Place a clean cover-glass over the material. In placing 
the cover-glass, do not drop it flat upon the drop of water, but 
place one side of it down first and allow it to squeeze the water 
along under it. 
4. Keep the top of the cover-glass dry. 
When filamentous algze or molds are to be examined, the 
material tends to cling together and must be carefully separated, 
in the drop of water, with dissection needles before the cover- 
glass is placed over the material. In case a coarse ground drug is 
to be mounted, the coarser particles should be first crushed in 
the water on the slide and subsequently teased apart with dissec- 
tion needles. 
Care should always be taken to see that the water or mounting 
medium used is not contaminated with foreign substances. This 
can best be practiced by examining the mounting medium under 
the microscope before the material to be examined is placed in it. 
Tur TecHuNniqgue oF MAkinc PerMANENT Mounts 
1. Tue Mountinc Meprum.—When a microscopic object is 
to be preserved permanently it must be kept from decaying 
and the fluid in which it is placed must be kept from evaporating. 
These conditions can be met by adding an antiseptic (2 per cent. 
