Other useful items include forceps, scalpels, 
sieves, petri dishes, measuring graduates, 
metal scoops or funnels, and shallow enamel 
pans. Funnels covered with bolting cloth are 
used to strain fine materials. An oven is helv- 
ful for drying materials. 
The work is time consuming and tiresome, so 
good equipment, situated in comfortable 
surroundings, is important for obtaining good 
results. 
Reference Materials 
There is no substitute for a good reference 
collection. Its size should depend on the scope 
of the study. Preliminary observations and 
familiarization with the animal and its feeding 
behavior are also necessary. A reference collec- 
tion may be made while collecting feeding be- 
havior and food-availability data. All materials 
in a reference collection, regardless of size, 
should bear authentic identification. 
Reference collections for forage identifica- 
tion studies should include not only herbarium 
specimens of plants, but also collections of 
seeds, buds, and underground parts such as 
bulbs and tubers. For most studies conducted 
over several months’ time, it will be necessary 
to collect plants in various stages of develop- 
ment. Collections at different times during the 
year are also necessary to be sure early- and 
late-maturing species are included. 
Preparation of Reference Materials and Unknowns 
Many animals grind their food into very 
small fragments. Reference material must 
be prepared so it illustrates microscopic 
characteristics. Baumgartner and Martin 
(1939) published a paper on the use of plant 
histology as an aid in squirrel food habits stud- 
ies. Kelso (1934) also used this method in 
studying pocket gopher stomach contents. Dusi 
(1949) discussed methods for the determina- 
tion of food habits by plant microtechnique 
histology and their application to food habits 
of cottontail rabbit. Others who have used this 
microscopic technique include Keith, Hansen, 
and Ward (1959), Ward (1960), Ward and 
Keith (1962), and Myers and Vaughan (1965) 
on pocket gophers; Davies (1959) on identifi- 
cation of grasses in leafy stage; Mulkern and 
Anderson (1959) and Brusven and Mulkern 
(1960) on grasshoppers; Williams (1962) on 
microtine mammals; Heady and Torell (1959) 
and Martin (1955) on sheep; Lesperance et al. 
(1960), Ridley et al. (1963) on steers and heif- 
ers; and Van Dyne and Heady (1965) on cattle 
and sheep. 
Techniques for preparation of reference ma- 
terials for feces examinations are usually the 
same as those used to identify stomach con- 
148 
tents. Hercus (1960), Storr (1961), Stewart 
(1965), and Stewart (1967) present descrip- 
tions of procedures they used. In some cases, 
reference materials were prepared from plants 
after they had passed through the animal. 
Various methods have been used to make mi- 
croscopic slides of reference materials. Dusi 
(1949) described in detail methods for mount- 
ing plant epidermis that could and could not 
be removed by mechanical means. He used rin- 
ses of Formalin-Aceto-Alcohol and stained the 
tissue in Mayer’s Haemalum, which was de- 
scribed by Johansen (1940). His slides were 
mounted in Apathy’s gum syrup as described 
in Richards (1943). 
Maceration slide mounts were made from 
plants whose epidermis could not be mechani- 
cally stripped off. Plant tissue was placed in a 
vial with equal parts of 10 percent nitric acid 
and 10 percent chromic acid, freshly mixed, 
heated at 40° C. for 6 to 24 hours (depending 
on the plant), rinsed in water, stained with 
Mayer’s Haemalum, and then mounted in Apa- 
thy’s gum syrup on glass slides. Baumgartner 
and Martin (1939) used Hertwig’s solution, a 
combination of clearing and mounting fluid. It 
can be prepared by using the following for- 
mula: 
19 ec. HC1 added to 150 cc. water 
60 ec. glycerine 
270 g. chloral hydrate crystals 
Croker (1959) macerated the leaves in 50 
percent nitric acid over a water bath, and the 
tissues were then washed in water to remove 
the acid. The cuticle was gently separated from 
the rest of the leaf with mounted needles and a 
camel-hair brush. It was then floated onto a 
slide with a fine jet of water and a brush. The 
slides were taken through the alcohol series 
from 15 to 95 percent, stained with 1 percent 
acid fuchsin, and permanently mounted in Eu- 
paral. 
A simpler method has been used by the au- 
thor to prepare reference slides. Leaf, stem, 
and root materials, from either fresh plants or 
herbarium mounts, were soaked in water until 
soft. A small segment of plant tissue was held 
on a glass slide and scraped on both sides with 
a sharp scalpel. A few drops of Hoyer’s solu- 
tion were applied, and the fine plant fragments 
were separated with a needle. 
Hoyer’s solution can be made by the follow- 
ing formula: 
20 percent gum arabic 
385 percent distilled water 
12 percent glycerin 
30 percent chloral hydride 
38 percent glucose 
For permanent mounts, these slides were 
heated in an oven at 40° C. for 48 hours. 
Williams (1962) stained materials with 1 
