88 
PLANTS OF YELLOWSTONE NATIONAL PARK 
7. Leaves hairy_____ Viola subvestita. 
7. Leaves smooth. 8. 
8. Plants dwarf, alpine.___ Viola bellidifoUa- 
8. Plants larger, not alpine____ Viola adunca. 
In addition to the above species, Canada violet ( Viola canadensis ), 
V- montamensis , and V. venosa have been reported as having been 
found in the park. 
LOASA FAMILY (LOASACEAE) 
A rather small family of herbaceous and more or less rough-hairy 
plants. The flowers are perfect with the parts attached above the 
ovary, and the stamens are usually very numerous. 
Mentzelia decapetala.—A. stout, rough-hairy plant seldom over 2 
feet high. The leaves vary from oval to oblong and are variously 
cut and lobed. The flowers are large, solitary, and terminal. There 
are 10 petals, which are white or yellowish and about twice as long 
as the calyx-lobes. The stamens are very numerous, 200 to 300. 
Mentzelia nuda is more slender and less hairy and grows 1 to 5 
feet tall. Its leaves are lance-shaped and sharply and deeply toothed. 
The seeds of this species are winged, while those of the preceding 
species are not. 
Mentzelia laevicaulis is a stout plant, 2 to 3 feet tall, with very 
large, light yellow flowers. 
Mentzelia alhicaulis grows from 4 to 12 inches high. The stems 
are nearly smooth and become white and polished as they mature. 
The leaves are lance-shaped or linear and vary from entire to deeply 
lobed and toothed. The flowers are small and yellow with 5 petals 
and 20 to 40 stamens. The seeds are numerous and rough. 
Mentzelia dispersa is similar except that the seeds are smooth. 
Mentzelia compacta is more branched than the preceding species, 
and the leaves are all entire. The flowers have only 15 stamens and 
the fruits only 10 or 12 seeds. 
The genus is commonly known as stickleaf. 
CACTUS FAMILY (CACTACEAE) 
This is a large, strictly American family and contains a great 
variety of unique and peculiar, mostly desert plants. The stems are 
thick, fleshy, green, and usually leafless. The parts of the flower are 
attached above the ovary, and there are numerous sepals, petals, and 
stamens and one pistil with several or many stigmas. The famify 
is represented here only by the Pricklypear ( Opuntia polyacantha) 
which is variable but easily recognized. It is found mostly in the 
region between Mammoth Hot Springs and the North Entrance. 
The stems consist of flat, very fleshy, more or less rounded joints 
