Orange, fruit of, 305 
peel, cross section, 148 
stamens of, 277 
Orcein, 416 
Orchid family, 494 
Orchidaceae, 494 
Orchidales, 494 
Orchidea, 495 
Orchids, Fig. of pollinia, 282 
floral organs of, 494 
parenchyma of, 116 
stamens of, 275 
Orchis mascula, 496 
Orchis militaris, Fig. of flower, 272 
Orchis morio, 496 
Order, defined, 327 
Ourouparia Gambir, 605 
Outline of plant groups, 328 
Ovary, 284, 473 
of Poppy, 528 
Ovule, amphitropous, 287 
anatropous, 287, 473 
INDEX 
Ovule, campylotropous, 287 
forms of, 287 
287 
Ovules, 285, 448, 473 
Ovum, 69, 450, 474 
Oxalic acid, production by molds, 394 
Oxidizing enzymes, 104 
Oxytropism, 34 
Pachystima, 552, 553 
Padus, 535 
Palaguium, 581, 582 
Panax quinquefolium, 576 
repens, 576 
Pandanus, roots of, 161 
Pandorina, 338 
Panicle, 258, 259 
Pansy, 566 
Papain, 103, 567 
Papaver, 524 
calyx of, 267 
latex of, 101 
placentation in, 288 
Papaver Rhoras, 528 
Papaver somniferum, 101, 627, 628 
Papaveracea, 524 
Papaverales, 524 
Papaverine Hydrochloridum, 527 
Papaveris Fructus, 528 
Papaw, 567 
Papaw Family, 566 
Papayin, 103 
Papilionacea, 537, 638 
