238 CACTACEAE. 



succulent, covered with spines. Seeds black; endosperm 

 none; embryo straight or curved. 



1, C. emoryi Engelm, Stems spreading, branching from the 

 base, cylindric, with 16-20 ribs, closely set with prominent hemi- 

 spheric areolae, bearing numerous thin straight yellow interlocked 

 spines; radials 40-50, very slender; central solitary, stouter and 

 much longer; flowers greenish yellow, 3-6 cm. broad, crowded on 

 one side near the end of the branches; fruit globose, very spiny, 

 3.5 cm. in diameter; seeds obovate, acutely keeled, shining and 

 minutely tuberculate, 2.4-2.8 mm. long. 



Said to occur frdm San Diego to the Salinas Valley, but we have 

 not seen it north of San Diego. Tia Juana. 



2. OPUNTIA Mill. 



Plants with flat or cylindric more or less tuberculate 

 joints and conspicuous but caducous leaves. These each 

 with an axillary areole, which is usually clothed with 

 soft wool intervened with barbed bristles at the upper 

 edge and usually bearing spines at the lower edge. 

 Flowers developed from the bristle-bearing part of the 

 areole, with rotate corollas. Ovary covered with 

 caducous leaves bearing axillary wool and often bristles 

 and spines. Fruit dry or succulent. Seeds large, flat- 

 tened and discoid, often margined, whitish; cotyledons 

 foliaceous, curved about the endosperm. 



Joints flattened. ( Prickley Pears.) 



Areoles 35-50 mm. apart. 1. 0. occidentalis. 



Areoles 25 mm. apart. 2. 0. littoralis. 

 Joints cylindrical. (Cholla.) 



Petals greenish yellow. 3. 0. hernardina. 



Petals deep red. 4. 0. prolifera. 



1. O. occidentalis Engelm. Erect and spreading, 1-3 m. high, 

 usually forming thickets; joints often 3 dm. long and 2 dm. wide; 

 areoles remote, about 4 cm. apart, with very fine closely set bristles, 

 1-3 white (dusky at base) deflexed spines; fruit sour, very juicy; 

 seeds 5-6 mm. broad, their margins crenulate. 



Frequent in our valleys and foothills from Los Angeles eastward. 



2. O. littoralis (Engelm.) Britton & Rose. Erect or spreading, 

 about 10 dm. high; joints often 30-45 cm. long and 20-25 cm. wide; 

 areoles usually about 2.5 cm. apart; spines straw color (dusky at 

 base), deflexed, slender; seeds 3-4 mm. broad, their margins undu- 

 late. 



Frequent on bluffs along the seashore. 



3. O. bemardina Engelm. Stems erect or nearly so, loosely 

 branched, slender, 6-15 dm. high, with reticulate wood; joints 



