of certain grasses. The study of burrow contents has been especially
illuminating and valuable.

All of the stored material from 22 dens on the Range Reserve and from 2
near Albuquerque, N. Mex., has been saved and analyzed as to species as
carefully as the conditions of storage would permit. Within the mound
the food stored is usually more or less segregated by plant species,
though the stores of material of any one kind may be found in several
places through the mound, and often the material is mixed. In the latter
case the quantities of the various species can only be estimated, but in
the former the species may be kept separate by the use of several bags
for collecting the seeds, and a fairly accurate laboratory weighing can
be made later. Very frequently, the explanation of this separation of
species lies in the different seasons of ripening, but sometimes where
two species are ripe at the same time near the mound, one is worked upon
for a time to the exclusion of the other. The one kind is often packed
in tightly against the other, but with a very abrupt change in the
character of the material.

A number of the more interesting and representative results of the
weighing and analyses of burrow contents are presented herewith in
tabular form. The data for each den, or lot, shows in grams the quantity
of stored material removed and the best estimate it was possible to make
of the percentages or weights of the various species. When the weight
was less than 5 grams, the mere trace of the species frequently is
indicated in the following tables by the abbreviation "Tr."

TABLE 1.--_Analyses of plants stored by _Dipodomys spectabilis
spectabilis_ Merriam, obtained from examination of representative dens
(all except Den 24 from U. S. Range Reserve, near the Santa Rita