OPUNTIACEAE. 815 
white above, about 5 cm. long: fruit scarlet, subglobose, 16-18 mm. in diameter : seeds reni- 
form, 2.4-2.8 mm. long, black, smooth and shining or minutely pitted. 
On prairies, south-central Texas and adjacent Mexico. 
4. Echinocactus Wrightii (Engelm.) Small. Stems ovoid or oval, 7.5-15 cm. 
high, 5-8.5 cm. thick, the ribs 13, with interrupting tubercles grooved to the base : spines 
various ; radials about 8, 3-5 cm. long, the upper straight, flattened, the 3 lower hooked, 
terete, darker than the upper; central solitary, 5-15 cm. long, erect, straw-colored with a 
dark tip, zigzag, hooked : flowers dark purple, 2.5-3.5 cm. long: fruit reddish, 1.5-2.5 
cm. long, fleshy : seeds flattened, curved, 1.4-1.6 mm. long, tuberculate, keeled along the 
back. [ÆE. uncinatus var.? Wrightii Engelm.] 
In dry soil, along the Rio Grande, Texas and adjacent Mexico. 
5. Echinocactus Muhlenpfórdtii Fen. Stems globose-ovoid to oblong-cylindric, 10- 
20 cm. high, the ribs often 13, more or less oblique: spines various; radials 10-12, subu- 
late, bristle-like, 12-32 mm. long, the upper longerthan the lower ; central solitary, firm, 
25-35 mm. long, hooked: flowers 5-7 cm. long, yellow and scarlet within: fruit globular, 
red, 8-10 mm. long. 
In sandy soil, Texas and adjacent Mexico. 
5. OPUNTIA Mi 
Fleshy plants, with conspicuously jointed stems, the joints flat or terete. Leaves scale- 
like, caducous, spirally arranged. Areolae axillary, usually spine-bearing. Flowers lateral, 
arising from the cushions of remote bristles of the areolae. Hypanthiun bearing areolae, 
not prolonged beyond the ovary. Sepals spreading, inseveralrows. Petals forming a rotate 
corolla. Ovary 1-celled: style cylindric: stigma 5-8-lobed. Berry more or less pear- 
shaped, fleshy or sometimes dry. Seeds flattened or disk-like. Embryo curved around 
the endosperm. PRICKLY PEAR. 
Joints flat. 
Spines wanting. 1. O. Ficus-Indica. 
Spines present, sometimes deciduous. 
Fruit fleshy. 
Spines flattened. 
Stems erect. 
Plants usually less than 12 dm. tall: flowers mostly over 7.5 cm. 
road. 2. O. Tuna. 
Plants usually over 12 dm. tall: flowers mostly less than 7.5 cm. S 
broad. 3. O. Engelmannii. 
Stems procumbent. 4. O. tortispina. 
Spines terete or nearly so, sometimes barely angled. 
Flowers over 5 cm. broad. 
Joints mainly over 12 cm. long: flowers over 11 cm. long. 
Joints mainly less than 12 cm. long: flowers less than 9 cm. long. 
Roots fusiform or tuberous. 
Joints narrowly obovateor oblong-obovate : species campes- 3 
trian. ; Ld 6. O. macrorhiza. 
Joints broadly obovate or orbicular-obovate : species Floridian. 7. O. austrina. 
8 
9 
g 
0. grandiflora. 
Roots fibrous. " 
Spines white tinged at the ends. . O. humifusa. 
Spines brownish black. . O. fusco-atra. 
Flowers less than 5 cm. broad. 2 : 
Spines less than 2.5 cm. long: joints about twice as long aswide, or 
$0 hick 11: 0. Pis Corvi 
i : joi times as long as thick. . O. Pes- : 
Fruit cee over 2.5 em. long: joints many ti g To ME 
Joints terete, slender. 13. O. leptocaulis. 
_1. Opuntia Ficus-Índica (L.) Mill. Stems erect, 12-18 dm. tall, proliferous : trunk 
cylindric, woody in age, the joints thick, obovate to elliptic, 10-15 cm. long, with the 
cushions of bristles immersed, spineless or sometimes with a very short spine: flowers 
yellow, 7.5-10 em. broad: fruit obovoid, bristly, 5-6 cm. long, edible, the pulp red. 
In sand, peninsular Florida and the West Indies. 
2. Opuntia Tüna (L.) Mill. Stems erect, 9-12 dm. tall, proliferous, the joints oval 
or elliptic, 10-20 em. long: cushions or bristles remoteabove, a cluster of 4—6 short rigid or 
subulate yellow spines, varying from very short to 3.5 cm. in length : flowers yellow or red- 
dish yellow, 7.5-10 cm. broad : fruit rather pear-shaped, 5-6 cm. long, edible. 
In sandy soil, peninsular Florida, the West Indies and Central America. 
3. Opuntia Engelmánnii Salm-Dyck. Stems erect, 12-18 dm. tall, forming a woody 
trunk, sometimes 15 cm. thick and clothed with a grayish bark, the joints ale green, 
obovate or orbicular-obovate, becoming 30 cm. long and sometimes 22 cm. broad ; cushions 
of bristles remote : spines few, 2.5-3.5 cm. long, or some shorter, flattened or angled, straw- 
