COULTER AND ROSE—NORTH AMERICAN UMBELLIFERAE. 181 
‘‘pinnae,’’ ‘‘segments,”’ ‘ultimate divisions,” ete., are purely arbitrary and difficult 
of application. 
There is great variation in the development of dorsal and intermediate wings. The 
laterals are always present, and have the characteristic thick and corky structure, 
but the dorsal and intermediate ribs may all be winged, or only some of them may 
be winged, or they may bear no wings at all, and these variations may occur even in 
the same plant. 
The presence of an involucre is also often a matter of uncertainty. In the usual 
sense there is no involucre in the genus, but in some of the species a vestige in the 
form of a low sheath is apparent. Occasionally this sheath becomes toothed, and in 
C. fendleri and C. newberryi the teeth are sometimes produced into narrow bracts. 
Two very natural sections of the genus are evident; the one with a compact head- 
like umbel and white flowers, the other with an open umbel and yellow flowers. 
In the more technical characters C. globosus is the most exceptional species, with 
its solitary oil tubes and small involucellate bractlets, but in its combination of 
characters it can not be separated from the other species. 
Umbels globose; flowers white; involucre wanting. 
Oil tubes several in the intervals. 
Fruit glabrous. 
Involucels of linear entire bratlets; fruit orbicular, not exceeding 8 mm. in 
diameter. 
Leaf segments small and narrow; fruit 6 to 8mm, in diameter. 1. C. acaulis. 
Leaf segments shorter and more obtuse; fruit larger ...--.---- 2. CL parryi. 
Involucels of broad more or less cleft bractlets; fruit broadly oblong, 10 mm, 
long ....2-.------- 2-2 eee ee eee eee eee eee eee ee 3. C. leibergii. 
Fruit puberulent at apex ...-..--------------------+++---- 4. CL megacephalus. 
Oil tubes solitary in the intervals........-.------------++++-+---- 5. C. globosus. 
Umbels open; flowers yellow; a vestige of an involucre and sometimes bracts. 
Leaf segments narrow......------------- 2-222 - eee eee eee eee eee 6. C. fendleri. 
Leaf segments broad ......-------+----+-------- 2-2-2 rere e rece 7. C. newberryi. 
1. Cymopterus acaulis (Pursh) Rydberg, Bot. Surv. Neb. 3: 38, 1894. 
Selinum acaule Pursh, Fl. 2: 752. 1814. 
Thapsia glomerata Nutt. Gen. 1: 184, 1818. 
Cymopterus glomeratus DC. Prodr. 4: 204. 1830. 
Cymopterus conpestris Torr, & Gray, Fl. 1: 624, 1840. 
Low (7 to 20 em.) and glabrous, with a short caudex bearing a clus- 
ter of leaves and peduncles; leaves merging from pinnate to bipinnate; 
ultimate segments mostly small and narrow; peduncles mostly shorter 
than the leaves; rays and pedicels very short, making a rather com- 
pact cluster; involucel of linear and entire more or less united foliose 
bractlets: flowers white; fruit 6 to 8 mm. in diameter, with 3 to 5 
broad wings on each carpel; oil tubes small, 4 to 8 in the intervals (or 
double the number where a rib has been suppressed), 8 to 14 on the 
commissural side. 
Type locality. ‘tin upper Louisiana;” collected by Bradbury; type 
specimen said by Pursh to be in Herb. Bradbury. 
Dry plains from Arkansas to Colorado on the south, and extending 
northward into the great plains of Canada. 
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