454 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
guilla), a congener of the mescal but a smaller plant, yields a fiber 
which is twisted into rope and twine in Mexico. It covers-many 
miles of the desert of western Texas, although in that region little 
effort has been made to utilize it. It barely reaches southern New 
Mexico and can never be of economic importance here. 
Recent advances in the price of rubber, caused by its increased use 
in manufactures, have stimulated a search all over the world for 
rubber-yielding plants. A large and profitable industry has been 
developed in northeastern Mexico in the extraction of rubber from 
one of the Composite known as guayule (Parthenium argentatum). 
It has been reported repeatedly that guayule occurs in New Mexico, 
but such statements are not supported by investigations. Although 
the sections of the State where it might be expected to grow have 
been carefully explored by botanists searching for it, not a single 
plant has been found. Another species of the genus, mariola (Par- 
thenium incanum), from which rubber can be extracted, does occur 
in New Mexico on the dry limestone hills near the southern border. 
It is said to yield a fair quality of rubber, but a lower percentage of 
inferior value to that obtained from guayule. Nowhere in the State 
is it found in sufficient quantity to be of commercial importance. 
Another member of the same family, the Colorado rubber plant 
(Hymenoxys floribunda) is abundant in northern New Mexico, where it 
covers hundreds of acres on the low foothills or higher up among the 
pine trees, sometimes to the exclusion of almost all other herbaceous 
vegetation. By chewing some of the stems for a few minutes a small 
mass of crude rubber is obtained. A few years ago a company was * 
formed in Colorado to extract rubber from the plant, but the under- 
taking was not a success. While there is no doubt that rubber can 
be gotten from this source, it is questionable whether a large enough 
supply could be relied upon to make extensive operations practicable. 
A prominent feature of the desert flora of the Southwest, along the 
rocky hills or advancing upon the plains, are the stately Agaves,«gen- 
erally known as mescal or century plants, several species of which 
are at home in New Mexico (pl. 10). Their leaves are broad and short, 
never more than 18 inches long, succulent, forming a compact rosette. 
Each is tipped with a sharp dark spine and is armed along the edges 
with stout hooked prickles. The tall flower stalks of our native 
species are 10 to 15 feet high or more, surmounted by thick divergent 
branches bearing hundreds of yellowish flowers. It is a popular 
belief that the century plant blooms but once, when it has rounded 
out a hundred years, hence the common name. A possible basis for 
this reputation is that in cultivation the plants seldom flower, 
although in their native haunts flowering plants are of common 
occurrence. They are known to bloom long before they attain the 
century mark and probably require only a comparatively few years 
