AMERICAN SUMAC. 11 
mac leaves and leaf stems, whereas in commercial practice the ex- 
traction generally is made on the unground leaves and stalks, and 
consequently is not so thorough, especially in the case of the larger 
stalks. This practice of making extraction on the unground leaves 
and stalks undoubtedly accounts for the comparatively high per- 
centages of potassium oxid in the samples of commercially extracted 
stalks, analyses of which are given in Table 5. 
Except for the organic matter which it contains, extracted sumac 
has comparatively little value for the farmer. However, in sections 
where sumac is gathered, where the land is usually deficient in or- 
ganic matter, the extracted material can be profitably hauled a mile 
or two, especially if before scattering on the land it can be mixed 
and rotted with barnyard manure. 
CAUSES OF POOR QUALITY IN SUMAC. 
Lack of care and attention to details in gathering and curing 
results in sumac of inferior quality. Undue exposure to the sun, 
any exposure to dew or rain, heating and molding in deep layers, 
and failure to turn once a day while curing cause decided darkening 
of the leaves and materially reduce the percentage of tannin. The 
presence of stalks, red leaves, blooms, or berries in cured sumac is 
objectionable, because they produce an undesirable color on leather. 
Furthermore, since the stalks contain only about one-fourth as much 
tannin as the leaves, their presence gives the mixture a lower tannin 
content. The presence of dirt or sand in cured sumac also is ob- 
jectionable, for it increases the weight without increasing the tannin 
content, and leathers tanned with such sumac will darken because 
of the iron present. 
COOPERATION FOR BETTER SUMAC. 
One of the objects of this bulletin is to point out the necessity for 
helpful cooperation between gatherers, dealers, and extract makers, 
with a view to the production of higher grade sumac and sumac 
extracts and the payment of higher prices to the gatherers for better 
sumac. This cooperation can be successfully maintained only if it 
is mutually beneficial. The initiative and success rest with the final 
buyers, the extract makers, who, by offering a bonus for " extra " 
quality sumac, can encourage the gatherers to make special efforts 
to produce a high-grade, bright, clean product. It is suggested 
that, for the information and guidance of gatherers, dealers and 
buyers keep on hand suitable samples, one to be known as " Stand- 
ard," for which they will pay the regular price, and another as 
" Extra," for which a bonus will be paid. Sumac materially below 
