. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 396 ANGIOSPERMAE—MONOCOTYLEDONES provided with a nectar-guide, forms a convenient alighting-platform for insects. Its cylindrico-conical spur does not secrete nectar, but affords a liquid' enclosed in cellular tissue to visitors, which extract it by boring. The two anther-lobes are firmly united with the column, each possessing a special adhesive disk covered by a bursicula. There is a rostellum between the two anther-lobes, which presses them apart; they de
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 396 ANGIOSPERMAE—MONOCOTYLEDONES provided with a nectar-guide, forms a convenient alighting-platform for insects. Its cylindrico-conical spur does not secrete nectar, but affords a liquid' enclosed in cellular tissue to visitors, which extract it by boring. The two anther-lobes are firmly united with the column, each possessing a special adhesive disk covered by a bursicula. There is a rostellum between the two anther-lobes, which presses them apart; they dehisce in the front by means of a longitudinal slit from top to bottom, the front of the poUinia being thus exposed; these contract into a sort of stalk towards the base and are here united to the epidermis of the Fig. 364. A. Flower of Orchis maculata, L, (after F. MacLeod). (i, 2, 3) The sepal and upper petals which make up a protective roof. (4, 5) Lateral sepals. (6) Labellum. (6 s) Lateral lobes of do. k^ bursicula; hb^ uppermost part of protective roof; sp, entrance to the spur; st^ stigma; jr, open anther locuius with pollinium ; i'/, membranous appendage of A. B. Pollinium of <9rc^z'5 ;2,Z-0« MacLeod after Darwin), a, immediately after withdrawal from the anther (on a pencil); ^, do., bent forward, after exposure to the air. An insect inserting its proboscis into the spur strikes its head against the bursicula, the epidermis of which is ruptured, so that the two small, circular adhesive disks at the ends of the poUinia cling to the visitor's head and become firmly fastened to it by the immediate hardening of the viscid substance. On withdrawing its head from the spur the insect thus removes the pollinia; the pollen-masses are drawn out of their receptacles and harden in the open air, their caudicles bending more and more forward. (This process can easily be imitated by means of a small sharp style or pencil.) The pollinia ultimately turn throu
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