AGAVES OF THE UNITED STATES. 53 
mucilage, saponin and salts which hold water in solution 
with great tenacity, and enable the plants to survive through 
long protracted seasons of dryness incident to a land of 
almost perpetual sunshine. Like other plants with a well 
developed aqueous tissue, they may be justly compared to 
camels, the ships of the desert." 
Most species are armed with stout spines, marginal 
prickles, corneous margins, or dry fibrous filaments. These 
render efficient protection against the attacks of hungry 
and thirsty animals, who would gladly seize upon their 
juicy and nutrient substance. 
Agaves usually grow slowly. In their natural habitats 
some attain maturity in three or four years, while others 
require ten to fifteen years or more. Taken from their 
homes and placed under new and strange conditions, they 
seldom make an effort to bloom. Although they respond 
to care, and grow into fine plants much prized in decora- 
tion, so rarely are their flowers seen that they have long 
been called *' Century Plants," because of the old idea 
that they bloom once in a hundred years only. 
When the period of inflorescence arrives, a great change 
is observed. The newer leaves are successively smaller and 
narrower; the central bud thickens, and after a season 
begins to shoot upwards with marvelous rapidity. What 
at first appear like narrow young leaves clustered around 
it, gradually become more and more separated by the elon- 
gating axis, and are seen to be bracts placed upon it at 
regular intervals. 
Dr. Engelmann* gives a fine description, accompanied 
with illustrations, of the flowering of A. Shawii at the Mis- 
souri Botanical Garden (Plates 44 and 47.) 
A plant here (Plates 62 and 63, Figs. 5, 6, 7), labeled 
A, horrida micracantha, commenced to send up a flower stalk 
early in November, 1894. Daily measurements of growth 
* Transactions of St. Lonis Academy, iii. 371. Collected writings. 
