5°2 
ONAGRACEAE 
I. Jussieneae : Jussieua, Ludwigia. 
B. Capsule as above. Axis prolonged. No bracteoles. 
II. Epilobieae (seed with hairy tuft) : Zauschneria, Epi- 
lobium. 
III. Hauyeae (seed with flat wing) : Hauya (only genus). 
IV. Onagreae (seed naked or with membranous edge or with 
small crown): Clarkia, Oenothera 
C. Nut. i — 4 seeds. Axis prolonged. No bracteoles. 
V. Gaureae: Gaura. 
D. Berry. Axis as in C. No bracteoles. 
VI. Fuchsiecie: Fuchsia (only genus). 
E. Capsule. Sta. i or 2. No bracteoles. 
VII. Lopezieae : Lopezia. 
F. Nut, hooked. Fir. dimerous. 
VIII. Circaeeae: Circaea (only genus). 
[Benth.-Hooker unite Trapa to O. and place the order in Myrtales; 
Warming places it in Myrtiflorae.] 
Oncidium Sw. Orchidaceae (28). 300 sp. trop. Am. Epiphytes 
(p. i73)* Some sp., e.g. O. Papilio Lindl., have flat tubers which 
make humus-collecting niches against the support ; others have fleshy 
leaves and no tubers. 
Onobrychis Linn. Leguminosae (ill. 7). 80 sp. temp. Eur., As. Floral 
mechanism as in Trifolium. O. sativa Lam. is the sainfoin, one of 
the best forage plants for a chalky soil. 
Onoclea Linn. Polypodiaceae. 3 sp. N. Hemisph. 
Ononis Linn. Leguminosae (ill. 4). About 80 sp. Medit., Eur. (3 in 
Brit. — rest-harrow). Shrubs and herbs, sometimes with thorny 
lateral branches. The mechanism of the firs, is intermediate between 
that of Lotus and that of Trifolium. At first the upper edges of 
the keel cohere, and the pollen is squeezed out at the tip as in Lotus ; 
afterwards the keel splits and the anthers emerge as in Trifolium. 
Cleistogamic firs, occur in some sp. 
Onopordon Linn. Compositae (xi). 20 sp. Eur., N. Afr., W. As. 
O. Acanthium L., the cotton thistle, in Brit. Leaves decurrent. 
Fir. as in Cnicus. 
Onosma Linn. Boraginaceae (iv. 4). 70 sp. Medit., Himal. 
Onychium Kaulf. Polypodiaceae. 4 sp. subtrop. 
Ophelia D. Don = Swertia Linn. 
Ophioglossaceae. Filicineae Eusporangiatae. 3 gen. with 17 sp. trop. 
and temp. They are all small herbaceous plants, some tropical 
species being epiphytic; there is a root-stock or rhizome bearing 
roots in acropetal succession, and giving off leaves which project 
above the soil. The leaf bases are usually fleshy and fit closely 
together concealing the stem. The leaf splits into a dorsal and a 
ventral part, the former being the ‘sterile’ green blade, the latter the 
‘fertile’ sporangiferous spike, often much branched and containing 
