31 
Oil-tubes solitary in the intervals. 
Stylopodium conical. 
Leaflets (at least the upper) linear to filiform. 
Involucre wanting; introduced. 
Flowers white 5 
Flowers yellow FcENicuiiXJM, o2 
Involucre present; flowers white (excepting Ammo- 
selinum). 
Low and diffuse, with ternately divided leaves. . Ammoselinum, B1 
Leaves finely oissected. 
Fruit linear-oblong; involucral bracts few and 
Tbepooakpus, 3 
Fruit ovate; involucre foliaceous Disoopleuba, 54 
Fruit ovate, 'tuberculate Leptooaulis, 53 
Leaves with few leaflets. 
Lateral ribs thick and corky; southern Oynosciadium, 28 
Ribs all filiform; western Oabem, 50 
Leaflets broader. 
Seed-face concave Ch^ebophyllum, 40 
Seed-face plane. 
Fruit oblong to orbicular Oiouta, 51 
Fruit linear-oblong Obyptot^nia, 52 
Stylopodium depressed. 
Flowers white. 
Fruit with all the ribs conspicuously winged Oymopteeus, 18 
Fruit with equal, broad and corky ribs, and no 
strengthening cells. 
Fruit small (not over a line long), flattened later- 
ally 4G 
Fruit larger, ovoid-globose iElHUSA, 2.5 
Fruit with thick corky lateral libsand filiform doi- 
sals, all with strengthening cells; aquatic. 
Leaves reduced to hollow jointed petioles Cbantzia, 20 
Leaves pinnate or decompound: western CEnanthe, 27 
Fruit with obscure or obsolete ribs Apiastbum, 35 
Flowers yellow. 
Fruit with ribs conspicuously winged. 
Low and often cespitose, with finely divided 
leaves; western Cymoptebps, 18 
Tall and branching, with larger, more coarsely 
divided leaves Thaspium, 20 
Fruit with equal, broad and corky ribs; Rocky Mts. 
Low, cespitose; high alpine • -Obeoxis, 22 
Foot or more high; in the foot-hills Habboubia, 47 
Fruit with filiform ribs. 
Tall and branching, with broad leaflets; mostly 
eastern ZiziA, 49 
f 
