49 6 
OROBANCHE 
7 in Brit, (broom-rape). They are parasitic by their roots upon the 
roots of other plants, and have no green tissue of their own (p. 176). 
O. ramosa L. is common on hemp. 0. major L. ( O . elatior Sutton) 
on Centaurea &c. (in Brit.), O. minor Sutton on Clover. Some are 
confined to one host, e.g. O. Hederae Duby to ivy, others are more 
general in their attacks. 
Orobus (Tourn.) Linn. = Lathyrus Tourn. O. hirsutus L. = Z. hirsutus, 
O. niger L. =Z. niger , 0. pratensis Stokes = Z. pratensis ; O.sylvati - 
cus Baumg. ( 0. vernus L.) = Z. vermis ; O. tuberosus L. = Z. moiticinus. 
Orontium Linn. Araceae (in). 1 sp. Atlantic N. Am. 
Oryza Linn. Gramineae (vi). 6 sp. trop., the most important of 
which is O. sativa L., the rice plant, the chief food plant of the 
world. It is an annual about 1 — 6 feet high. The common rice is 
cultivated in hot steamy lowlands, and the fields are covered with 
water; the mountain form is cultivated up to 6000 feet without irri- 
gation. The grain in the husk is known as paddy. 
Osbeckia Linn. Melastomaceae (1). 50 sp. Old World trop. 
Osmanthus Lour. Oleaceae (1. 3). 10 sp. E. and S. As., Polynes., 
N. Am. O. fragrans Lour. (Olea fragrans Thunb.) is often cultivated 
in hot-houses ; it has an edible fruit, and its leaves are used to perfume 
tea. 
Osmunda Linn. Osmundaceae. 6 sp. temp, and trop. O. regalis L., 
the royal fern, is found in Brit. It has a root-stock bearing scale 
leaves below the soil and ordinary leaves above. The stock may 
sometimes be found a foot high, like the stem of a tree fern. The 
fronds are large (1 — 10 feet); the lower pinnae are vegetative, the 
upper are reproductive only and form a sort of panicle. They are 
densely covered with sori, which have no indusium and have a pecu- 
liar annulus consisting of a round group of cells at one side of the 
apex. The sporangium dehisces longitudinally. Other sp. have the 
fertile pinnae on the lower part of the leaf, others again have separate 
vegetative and reproductive leaves. 
Osmundaceae. Filicineae Leptosporangiatae (Homosporous). 2 gen. 
with 10 sp. trop. and temp. Short-stemmed ferns, with naked sori. 
The sporangia are shortly stalked and have an annulus, consisting of 
a roundish group of cells at one side of the apex ; they open by a 
longitudinal fissure. Genera : Osmunda (sori on special pinnae), 
Todea (sori on backs of ordinary pinnae). 
Osteomeles Lindl. Rosaceae (11. 4). 10 sp. Andes, Sandwich Is., &c. 
Osteospermum Linn. Compositae (ix). 38 sp. S. Afr. 
Ostrowskia Regel. Campanulaceae (1. 1). 1 sp. Turkestan. 
Ostrya Mich, ex Linn. Betulaceae. 2 sp. N. temp. Like Carpinus. 
O. virginica Willd. (lever-wood) furnishes a hard wood. 
Othonna Linn. Compositae (vm). 80 sp. S. Afr. Xerophytes (p. i6 t ) 
with swollen roots and often fleshy leaves. 
Ouratea Aubl. = Gomphia Schreb. 
