112 MISC. PUBLICATION 303, U. S. DEPT. OF AGRICULTURE 
Covillea glutinosa, see Covillea tridentata. 
Covillea tridentata (DC.) Vail. Creosotebush. 
C. glutinosa (Engelm.) Rydb., Larrea mewicana Moric., L. glutinosa En- 
gelm., L. tridentata (DC.) Cov., L. tridentata glutinosa Jeps. 
Range: 9, 10, 11, 16, 17. 
Site: Dry, sun. 
Fruit: Capsule. 
A small to large evergreen shrub; slow growing; sparsely branched and with 
thin foliage, especially when older; inhabits the most xeric areas in North 
America; makes successful and persistent growth in thin bodies of soil over 
layers of hardpan; transplants ordinarily require considerable water to start 
them growing; very inflammable. 
Stomach records: Gambel quail. Observations: Texas antelope squirrel, jack 
rabbit. Not eaten by livestock ; poisonous to sheep. 
Cowania alba, see Cowania stansburiana. 
Cowania davidsonii, see Cowania stansburiana. 
Cowania ericaefolia Torr. Heath cliffrose. 
Range: 11, 17. 
Site: Dry, sun. 
Fruit: Achene. 
A small, straggling, much-branched evergreen shrub found on _ limestone 
soils. 
Cowania havardii Wats. 
Range: 11. 
Site: Dry, sun. 
Fruit: Achene. 
A small, much-branched evergreen shrub. 
Cowania stansburiana Torr. Quinine bush. 
C. mexicana dubia Brandeg., C. davidsonii Rydb., C. mexicana stansburiana 
(Torr.) Jeps., C. alba Good. 
Range: 9, 10, 11, 13, 14. 
Site: Dry, well-drained, sun. 
Fruit: Achene, available in October. 
A small to large shrub or small to rarely large tree; evergreen; freely 
branched, stiff; flowers in June; increased branching occurs under grazing; 
seed germination 10-80 percent. 
Stomach records: Black-tailed deer. Observations: A staple food of mule 
deer. An important and valuable browse for cattle and sheep. Browsing to 
65 percent stimulates beneficially the reproduction of the plant; more than 80 
percent causes deterioration. 
Crataegus spp. Hawthorns. 
These species are small shrubs to small trees growing in many sites, in all 
kinds of soil, in all parts of the country, most of them being almost impossible 
of identification except by specialists. No effort is here made to Separate the 
various species. Somewhat more than 1,200 species have been listed for the 
country, the majority of these occurring in the northeastern United States; other 
studies have reduced this number to less than 100. Owing possibly to hybridi- 
zation and great variation, the actual number of species has not been deter- 
mined up to the present time. Nevertheless, these plants are of considerable 
value for erosion control and for wildlife food and cover. A great many of 
them are thicket forming and many species hold the fruit over the winter. Most 
species are thorny and provide a dense cover valuable for soil and wildlife 
alike. The best way in which to discover the utility of these species is to 
examine the wild forms occurring in any particular region and to collect such 
ones as seem to be able to grow on eroded sites and to produce the maximum 
amount of cover and food. 
Most species grow in neutral soil, often on very poor soils; young plants often 
form long taproots and hence are often difficult to transplant; 6,000—40,000 
seeds per pound, germination about 40 percent, about 2,500 usable plants per 
pound of seed; propagation is by seed stratified and sown in spring; alternate 
hosts for the cedar apple rust. 
