160 MISSOURI BOTANICAL GARDEN. 
Yucca is a small genus of evergreen leaved plants of the 
lily family, belonging to the Central American flora and 
that of the Southern United States, one species reaching 
well up into the Rocky Mountains. Engelmann recognized 
fourteen species, while Baker, who has also made the 
Yuccas the subject of much study, admits half as many 
more, several of the additional species having been called 
varieties by Engelmann, though several others are known 
only from plants in cultivation (few of which have 
flowered or fruited ), and are regarded by some botanists as 
probable forms or derivatives of other species known in a 
state of nature. 
While the more eastern of our species are short-stemmed, 
several of those native in the southwest become trees, often 
of considerable size and with thick rough bark. The fruit 
of the section with pulpy carpels is more or less eaten, and 
the fibers of the leaves are used for cordage by the Mexi- 
cans who also make a good deal of domestic use of the root- 
stocks as a substitute for soap. Some years since the 
proprietors of an English newspaper established a mill in 
the home of one of the tree Yuccas, intending to make 
paper pulp from its wood, but the enterprise was shortly 
abandoned. 
Like most of the monocotyledons, aside from the palms, 
Yucca has left few if any fossil remains complete enough 
for certain determination, and Professor Lester F. Ward 
informs me that only one fossil species has ever been 
referred to the genus Yucca, — namely Y. Roberti, Bureau; 
found in the Paris basin, — and that even this is generally 
considered to belong to Yuccites, a form assemblage, some 
of the components of which are of very early origin, but 
none of them of necessity closely allied to the existing 
genus Yucca, nor representing its ancestral type. 
The principal revisions of the genus are by Engelmann, 
in the Transactions of the St. Louis Academy, iii, pp. 17, 
210 and 371 (brought together, with additional descriptions 
and notes printed elsewhere by him, in his Collected Writ- 
