AN ADDITIONAL TREE-YUCCA AND ONE OTHER SPECIES 
NEW TO THE UNITED STATES. 
BY WILLIAM TRELEASE. 
When my revision of the Yucceae was published, in 1902, 
fragmentary or aberrant specimens collected in the Bound- 
ary region about sixty years ago by Bigelow were tentatively 
referred to Yucca rostrata. Of recent years, plants that I 
cannot distinguish from these, but which appear to be dif- 
ferent from though closely allied to Y. rostrata, have been 
collected in western Texas by several botanists and though 
still incomplete the material that I have seen is sufficient 
for the characterization of this plant, which is dedicated to 
Mr. C. H. Thompson of the Missouri Botanical Garden, who 
has collected it on several occasions. 
Yucca Thompsoniana Trelease. 
Y. rostrata Trelease, Rept. Mo. Bot. Gard. 13: 68,— as to the 
Bigelow collection. 
Flowering while stemless but at length caulescent with a trunk 
about 1 m. high, more or less cespitose. Leaves linear to typically 
narrowly lanceolate and dagger-like, 4 to mostly 6-10 mm. X 18-25 
or exceptionally 35 cm., nearly flat, straight and rigid, bluish and 
somewhat glaucous, striate, more or less roughened on the back, 
pungent with a finally brown acicular spine, the minutely denticulate 
margin bright yellow. Inflorescence about 1 m. high, the upper half 
or more simply paniculate, more or less evanescently floccose or 
glabrous. Flowers with segments about 40 mm. long. Fruit capsular, 
erect, tardily dehiscent, narrowly ovoid, 20 X 40 mm., attenuate above 
into a slender fragile rather straight beak, the heavily obconical 
pedicel often bearing the reflexed segments of the dried perianth: 
exocarp at first waxy with a broad raised line down the rounded back 
of each carpel: seeds small, 4>< 6 mm., rather thin, dull. 
Texas and adjacent Mexico, in the region of the great 
bend of the Rio Grande, from Devils River to Presidio, 
Marathon and San Elizario.—Pl. 104-107. 
Specimens examined :—Below San Elizario (Bigelow, June 
14, 1852). Bufatello, near Presidio del Norte (Bigelow, 
August 10, 1852,—the type). Los Moros (Bigelow, Septem- 
ber 23, 1852). Langtry (Thompson, 156, 1909). Devils 
(101) 
