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Rh several funiculi, and each funiculus capable of producing several embryos, 572.

Piperaceæ very rare in equinoctial Africa, 149; explanation of the structure of their seeds, 452

Pittosporeæ, character of the order and observations on its distribution in Terra Australis, 13

Pistilla and Antheræ, analogy of composition in, 378—380 note; proved by the transformation of the one into the other in cases of monstrosity, 379 note

Pistillum of Phænogamous plants, observations on its composition, 269, 270 note; hypothetical view of the structure of the compound, 270 note; 299 note; relation of the single pistillum, and of the component parts of the compound to calyx and corolla, and to the axis of the spike, 292; relations of reduced pistilla, 292—291; complete number of pistilla and stamina equal to that of the divisions of calyx and corolla united, 293; this complete number equally rare in both the primary divisions of Phænogamous plants, ibid.; Monocaryum offers the only known example of reduction to a solitary pistillum in the great class Liliaceæ;, 299; its position in that section of Colchicum, 300; pistilla when of equal number usually placed opposite to the petals of Dicotyledons, and to the outer series of perianthium in Monocotyledons, 300

Placentæ, relations of stigmata and, 553—563; necessarily double, 556; their arrangement in the carpels, of various families and plants, 557-560; Cruciferæ, Papaveraceæ, Parnassia, Irideæ, 559; Orchideæ, 560-562; manifestly double and consequently marginal or submarginal in, 560; as in Monocotyledonous plants generally opposite to the three inner divisions of perianthium, ibid.; in Apostasia opposite to the three outer divisions, 560-1; in Scitamineæ, 561; placentæ of Orobancheæ double and submarginal, 562

Plantain of the banks of the Congo probably of Asiatic origin, 156

Plants, probable number of species in European Herbaria [in 1814], 7; proportion of Dicotyledonous' and Monocotyledonous in Persoon's Synopsis and in Terra Australis, 8; in the vicinity of the Congo, 101—106; how far this proportion is influenced by climate, 8, 102; proportion of Acotyledonous in Terra Australis, 9; in various parts of Europe, 9; in the vicinity of the Congo, 101—104; common to equinoctial Africa, America, and Asia, 164; to equinoctial Africa and America, but not found in India, 165; to equinoctial Africa and India, but not found in America, 165

Pleurothallis, spirally striated cells in, 515

Plumbagineæ, species in the collection from Central Africa, 297

Plurality of embryos in the seeds of Coniferæ, 565—575; constancy of, 568—572

Poaceæ, a tribe of Gramineæ, observations on the tribe and on its distribution in Terra Australis, 58

Podocarpus, structure of the ovulum in, 455; origin of the ovulum in, 458; analogy of male and female organs in, 461

Pollen, marginal production of, in the antheræ, 379 note; mucous tubes of, observed in Cytinus, 407-8; applied to the apices of the enlarged ovula, 408 note; of Cycadeæ, 459, 460; microscopic observations on the particles contained in the, 463—486; mode of action of the pollen in impregnation, 465-6, 475-6; in Asclepiadeæ, Periploceæ, and Orchideæ, 476; motion of particles of pollen seen by Needham and Gleichen, 477; observations of M. Brongniart, 478-9; occasionally in some plants continues long quiescent, 574-5; of Tradescantia Virginica, development of, 514 note.

Pollen grains, their structure in Asclepiadeæ, 524

Pollen tubes, their production and course in Orchideæ, 507—510; Asclepiadeæ, 525-8, 532; in other