COULTER AND ROSE—-NORTH AMERICAN UMBELLIFERAE, 25 
NATIVE GENERA AND SPECIES. 
1. HYDROCOTYLE L. Sp. Pl. 1: 234. 1753. 
Calyx teeth minute or obsolete. Fruit more or less orbicular, strongly 
flattened laterally. Carpel with five primary ribs, the dorsal marginal, 
broad or filiform; inter- 
mediates filiform (rarely 
obsolete), usually curved; 
laterals filiform or broad, 
distinct from those of the 
other carpel or confluent; 
a prominent  oil-bearing 
layer beneath the epider- 
mis, occasionally contain- 
ing small oil tubes, and 
usually a thick layer of 
strengthening cells sur- 
rounding the seed avity. FIG. Hydrocotyle cuneata: a, X 10; b, x 20. 
Low herbaceous peren- 
nials growing in or near water, with slender creepingstems, orbicular- 
peltate or reniform leaves, and small white flowers in simple or pro- 
liferous umbels without involucre. 
First species cited, JZ. vulgaris L. 
A genus widely distributed in both hemispheres, containing about 
75 species, 9 of which are found in the United States and Canada. 
Fruit with pericarp thin except at the broad thick corky dorsal and lateral ribs; 
involucre of short ovate bracts; leaves orbicular-peltate, crenate; peduncles 
as long as petioles, both from slender creeping rootstocks. 
Fruit notched at base and apex. 
Umbels simple ......-.---.------------- 2-2-0 eee eee eee eee 1. H. umbellata, 
Umbels proliferous. 
Umbels few. 
Dorsal ribs very obtuse; California...........------------ 2. H. prolifera. 
Dorsal ribs rather acute; Atlantic coast .......------------- 3. A. canbyi. 
Umbels numerous in a profusely branching inflorescence... 4. 1. bonariensis. 
Fruit not notched. 
Fruit not cuneate at base. 
Fruit subsessile .......2....-------------- eee eee ee ee eee eee 5. HH. verticillata. 
Fruit pedicellate.........--.------------- +--+ ++ 2 ee eee eee eee 6. H. australis. 
Fruit cuneate at base ...........-.-..-------------5-----++----- 7. H. cuneata. 
Fruit with pericarp uniformly corky-thickened and ribs all filiform; leaves not pel- 
tate; peduncles much shorter than petioles. 
Leaves thin, with short petioles; umbels subsessile. ......------ 8. H. americana. 
Leaves thicker, with elongated petioles; umbels peduncled .. 9. 1. ranunculoides. 
1. Hydrocotyle umbellata L. Sp. Pl. 1: 284. 1753. 
H. umbellulata Michx. Fl. Bor. Am. 1: 161. 1803, 
Descending branches of the rootstock with round tubers: umbels 
many-flowered, simple (rarely slightly proliferous); pedicels + to 12 
