OPUNTIA 
489 
the sporangia sunk in its tissues. The spores are all of one kind and 
give rise, as far as known, to subterranean colourless prothalli, living 
saprophytically. Genera: Ophioglossum (sporangia sessile, in two 
rows, forming a narrow close spike), Botrychium (sporangia in small 
crested clusters forming a long loose spike), Helminthostachys (spo- 
rangia peltate, borne on sporangiophores which arise from the two 
sides of the fertile spike). 
Ophioglossum Linn. Ophioglossaceae. 9 sp. trop. and temp. 0 . 
vulgatum L., adder’s-tongue, is found in Brit. The leaves are 
developed very slowly, one appearing above the soil each year. 
Adventitious buds are formed on the roots and thus the plant multi- 
plies vegetatively. The sporangiferous spike is usually unbranched, 
except in O. pabyiatuiii L., where “instead of a single spike there are 
a number arranged in two rows along the sides of the upper part of 
the petiole and the base of the lamina.” (This sp. and O. pendulum L. 
are epiphytic.) The roots most often arise in relation to the leaves, 
one appearing at the base of each ; they are commonly unbranched. 
Ophiopogon Ker-Gawl. Liliaceae (vm). 4 sp. Japan, China. The 
mucilaginous tubers of 0 . japonicus Ker*Gawl. are edible. [Hsemo- 
doraceae Benth. -Hooker.] 
Ophiorrhiza Linn. Rubiaceae (1. 2). 50 sp. trop. As., Indo-mal. 
Ophiurus Gaertn. f. Gramineae (11). 4 sp. trop. Included in Rott- 
boellia in Nat . PJl. 
Ophrys Linn. Orchidaceae (3). 30 sp. Eur., W. As., N. Afr. 
( 0 . apifera Huds., bee-orchis, O. aranifera Huds., spider-orchis, 
0 . muscifera Huds., fly-orchis, in Brit.). Terrestrial herbs with the 
habit and floral characters of Orchis. O. apifera is one of the few 
self-fertilising orchids. If the pollinia are not removed by insects (as 
in Orchis) they drop out of the anther and dangle on their long 
caudicles in front of the stigma, against which they get blown or 
knocked (see Darwin). 
Oplismenus Beauv. Gramineae (v). 5 sp. trop. and subtrop. 
Opopanax Koch. Umbelliferae (7). 2 sp. Medit. Gum opopanax is 
obtained from incisions in the roots. It is used in perfumery. 
Opuntia Tourn. ex Mill. Cactaceae (11). 200 sp. Am. Fleshy 
stemmed plants, usually with small fleshy leaves, which drop off very 
early (see order). In O. subulata Engelm. the leaves are large and do 
a good deal of assimilation. Some, e.g. O. Stapeliae DC., have mam- 
milla-like cushions ; O. brasiliensis Haw. has the main stem cylindrical 
and the lateral ones flat ; most sp. have all the stems flattened, e.g, 
O. vulgaris Mill, (prickly pear), 0 . Ficus-indica Mill. (Indian fig), die. 
(see Goebel’s Pflanzenbiol. Sch. 1. p. 73 seq.). The leaves of the 
lateral shoots usually form groups of thorns, but in O. diademata 
Lem. are ribbon-like and scaly. Mafiy are vegetatively propagated 
by the detachment of branches, e.g. O. fragilis Haw., which rarely 
flowers at all. The fruits of prickly pear &c. are edible ; some are 
