258 Cactaceae 
A. Biennials: flowers 2.5—-6.3 cm. long; each placenta with 2 rows of ovules; ovules 
separated by horizontal lamellae; capsule linear; petals 5 or 10. 
B. Leaves lanceolate; petals 10. 
C. Outer petals less than 5 cm. long; plant 2—2.5 dm. high; some of the anther- 
bearing filaments dilated. E. 
M. pumila Nutt. 
CC. Outer petals 5—6.2 cm. long; plant 6—9 dm. high; all of the filaments 
filiform. E. M. laevicaulis T. & G. 
BB. Leaves linear; petals 5. E. 
M. brandegei Wats. 
AA. Annual: flowers 0.31.6 cm. long; each placenta with | row of ovules; ovules 
not separated by horizontal lamellae; capsule oblong; petals 5. 
D. Seed tuberculate, more or less grooved along the angles; leaves usually sinuate- 
toothed. E. (M. dispersa.) M. integrifolia Rydb. 
DD. Seed smooth or striate. 
E. Flowers not bracted; seed 0.7—1.4 mm. long. E. (M. gracilenta; M. tener- 
rima.) M. albicaulis Dougl. | 
EE. Flowers conspicuously bracted with wide toothed bracts; seed almost 2 mm. 
long. E. M. congesta T. & G. 
CACTACEAE Cactus Family 
Stems fleshy, flattish or terete, often ridged or tubercled, continuous or jointed, gen- 
erally spiney, the spines arising from cushions of minute bristles. Leaves none or small, 
subulate. Flowers mostly solitary, sessile, terminal or lateral, perfect, regular, showy. 
Calyx many-lobed or of distinct sepals. Petals numerous, in several rows, mostly dis- 
tinct. Stamens numerous, on throat of calyx. Ovary inferior, |-celled; placentae several, 
parietal; styles terminal, united, elongated; stigmas many. Fruit mostly fleshy, some- 
times nearly dry. Seeds many, smooth, tubercled. 
A. Stems not jointed, ovoid, not branched; “‘eyes” raised on conspicuous tubercles. 
MamILLarIia (p. 258) 
AA. Stems jointed, branched; “‘eyes’’ not raised on tubercles. OPUNTIA (p. 258) 
MAMILLARIA BALL CACTUS 
Plants globose or somewhat cylindric; stems solitary or clustered, tubercled: tubercles 
conic or cylindric, woolly with clusters of spines at apex. Leaves none. Flowers usually 
in a transverse zone of the stem, in ours bright red or purple. Calyx-tube campanulate or 
funnelform, produced beyond the ovary which is often hidden between the tubercles; ex- 
terior calyx-segments ciliate (ours). Ovary smooth, ovoid or club-shaped or oval (ours) ; 
stigmas 5—/, radiate. Fruit smooth, ovoid (ours). (L. mamilla—a nipple; referring 
to the tubercles.) E. (Cactus viviparus.) 
“M. vivipara Haw. 
OPUNTIA OPUNTIA 
Stems jointed, branching; joints flat or cylindric. Leaves minute or none, deciduous, 
spirally arranged on the stem, mostly subulate; ‘‘eyes’ mostly spine-bearing. Flowers’ 
usually lateral. Calyx-tube not prolonged beyond the ovary; calyx-lobes spreading. Ovary 
cylindric, exserted; stigmas 2—7. Fruit pear-shaped, often spiny. (Grew in Greece 
near the town of Opuntia.) 
a 
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