EUPHORBIA, SECTION TITHYMALUS. 91 
ANALYTICAL KEY. 
I. Glands of the involucre with a rotund and entire margin. 
A. Leaves entire, seeds without a caruncle. E. telephoides, E. inundata. 
B. Leaves serrulate, seeds carunculate. 
‘a. Ovary and capsule smooth. 
1. Seeds ovoid, pointed at apex, rays 5. E. Helioscopia. 
2. Seeds globose lenticular, rays 3. E, leiococca. 
b. Ovary and capsule verrucose. 
1. Seeds smooth, rays 5 or more; perennial by a rootstock. 
E. Darlingtonii. 
2. Seeds smooth (sometimes faintly reticulate in E. obtusata), 
rays 3 to 5; annual. 
Pubescent, leaves acute, rays 3 to 5. E. platyphylla. 
Smooth, leaves obtuse, rays 3. EK. obtusata. 
3. Seeds reticulate, rays 3; annual or some biennial or perennial 
by crown buds. 
* Stems cymosely branched below the umbel, capsules short 
warted. 
+ Styles divided nearly to the base, leaves rotund or retuse at 
the apex. E. dictyosperma. 
+t Styles not divided below the middle, leaves acute or only 
obtuse. 
Most of the floral leaves longer than wide. 
E. Arkansana Missouriensis. 
Floral leaves about as broad aslong. 4. Arkansana. 
Many stemmed, floral leaves narrowly oblong. 
E. Mexicana. 
** Racemosely branched, capsules long warted; high mountain 
plants. E. alta. 
II. Margins of glands not rotund nor entire. 
A. Stem leaves decussate. E. Lathyris. 
B. Stem leaves alternate. 
a. Most of the floral leaves alternate ; trichotomously branched. 
E. trichotoma. 
b. Floral leaves opposite, rays dichotomous. 
1. Seeds not carunculate, involucres shorter than their peduncles, 
calyx 8-lobed. 
* Peduncles 5 to 12 mm. long, floral leaves cordate, glands 
wrinkled. E. Floridana. 
** Peduncles 1 to 3 cm. long, floral leaves rarely cordate, glands 
smooth. 
Leaves of the stem lance-linear. E. inundata. 
Leaves of stem oblanceolate to obovate. L£. telephoides. 
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