. A manual of botany. Botany. 186 ilANUAL OF BOTANY or arranged in a more or less regular manner. The pores may be either simple, or provided with Kttle Hd-Kke processes, as in the Passion-flower {fig. 388, o, o, o) and Gourd {fig. 389). These processes {fig. 389, o, o) are pushed off by corresponding projections of the intine, t, t, when the pollen germinates ; hence such pollen-grains have been termed operculate. In the pollen- grains of some of the Firs, the extine is expanded on two sides to form two curious bladder-like protuberances (fig. 391). The poUen-grains are usually free in the lo
. A manual of botany. Botany. 186 ilANUAL OF BOTANY or arranged in a more or less regular manner. The pores may be either simple, or provided with Kttle Hd-Kke processes, as in the Passion-flower {fig. 388, o, o, o) and Gourd {fig. 389). These processes {fig. 389, o, o) are pushed off by corresponding projections of the intine, t, t, when the pollen germinates ; hence such pollen-grains have been termed operculate. In the pollen- grains of some of the Firs, the extine is expanded on two sides to form two curious bladder-like protuberances (fig. 391). The poUen-grains are usually free in the loculi of the anther. Sometimes, though rarely, they adhere to a greater or less extent to each other. Thus we have groups of four in Periploca grceca, eight in Inga anomala ; or some higher multiple of four, FiCf. 392. Fig, Fig. Fij/. 392. Polliiiia, p, of a species of Orcliis with their caudicles, e, adhering to the retinacula, r, r. Fig. :I93. Pistil of a species of Ascleptas, witli the poUinia, p, adheriug to the stigma, s. h. Pollen-masses separated. Fig. 394. TJpper part of the flower of au Orchis, showing the pollinla adliering to the column by the retinacula, a. as in many species of Acacia. In the Onagracese, the pollen- grains are loosely connected by long viscid filaments or threads ; while in the Orchidaoeae those of each pollen-sac cohere together and form pollen-masses, to which the name oipollinia has been given {fig. 392, p). In the Asclepiadacese somewhat similar masses occur {fig. 393,^, and 6); but in the latter, the whole surface of each poUen-mass is invested by a special covering. By a careful examination of these pollinia we find that they are formed of definite masses agglutinated together, and when sepa- rated, each of these masses is found to consist of four pollen- grains. In the pollinia of the Orohidaceae we also find other peculiarities; each] is prolonged downwards in the form of. Please note that these images are extracted from scanned
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