AGW PROCEEDINGS OF THE AMERICAN ACADEMY 
3. Y. CANALICULATA, Hook. Caudex 6 to 25 feet high, branching 
at top: leaves very long (24 to 4} feet by 2 or 3 inches wide), straight 
and very rigid, deeply channelled, rough on the back: panicle subses- 
sile, ovate, 2 to 4 feet long, densely flowered, nearly glabrous, with 
large ovate or broadly lanceolate bracts: flowers cream-white ; seg- 
ments ovate or ovate-lanceolate, acute or acuminate, 1} to 24 inches 
long: filaments scarcely papillose, nearly equalling the pistil: style 
slender; stigmas narrow, deeply 2-lobed: fruit subcylindric, strongly 
beaked, 3 or 4 inches long: seeds 3 to 3} lines broad. — Bot. Mag. 
t. 5201. Y¥. Treculiana, Carr. Rey. Hort. 7. 280 (name only); Engelm. 
le. 41. VY. longifolia, Engelm.; Buckley, Proc. Philad. Acad. 1862, 8. 
Texas to Northern Mexico. 
++ ++ ++ Leaves coarsely filamentose on the margin. 
4, Y. BaccaTA, Torr. Caudex short or none: leaves very thick and 
rigid, 14 to 3 feet long by an inch or two wide, channelled or concaye, 
rough especially on the back, tipped by a very stout brown spine: 
panicle pedunculate, usually glabrous, with ovate-lanceolate or ovate 
bracts: perianth-segments narrow, 2} to 3 inches long: stamens 
equalling the ovary: style more or less elongated, slender: fruit 
oval or cylindric, 3 to 5 inches long, dark purple, often long-beaked: 
seeds 4 to 8 lines broad, a line thick or more. — Bot. Mex. Bound. 
221: Engelm. |. c. 44: Ill. Hort. 3 ser. t. 115. §. Colorado and W. 
Texas to S. California and Northern Mexico. 
Var. AUSTRALIS, Engelm. ].c. Caudex taller (often 10 to 50 feet), 
branching: leaves thinner and smoother, with finer fibres: flowers 
smaller (14 inches long), with ovate segments and short style. — The 
more southern Mexican form. 
d). Y. Scuorru, Engelm. 1.c. 46. Caudex 2 to 5 feet high, branched 
from the base: leaves straight, rigid, about 9 inches long by 6 or 8 
lines wide, concave, somewhat pungent, smooth, with very slender 
straight marginal threads: panicle loosely flowered, with flexuous 
peduncle and branches, and large lanceolate bracts: flowers rather 
small: style and stigmas short: fruit ovate, 2 inches long, shortly 
beaked. — S. Arizona. 
+ + Fruit becoming dry and spongy, indehiscent, erect : seeds thickish, smooth 
and scarcely margined, with entire albumen. Tall and branching, with 
sessile panicles and serrulate leaves. 
6. Y. BREVIFOLIA, Engelm. Caudex 15 to 30 feet high: leaves 
3 to 8 inches long by as many lines wide, very rough and rigid, atten- 
uate to a stout spine, nearly flat above: panicle pyramidal, with white 
