. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 276 ANGIOSPERMAE—DICOTYLEDONES comes into contact with the insect, getting cross-pollinated if this has previously visited another flower of the species. The first flower visited by an insect will be self-pollinated as the visitor backs out of it. Should insect-visits fail, automatic self-pollination of unexploded flowers is possible, and may be effective under certain conditions (vide infra). BurkiU (Proc. Phil. Soc, Cambridge, viii, 1894) aptly describes t
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 276 ANGIOSPERMAE—DICOTYLEDONES comes into contact with the insect, getting cross-pollinated if this has previously visited another flower of the species. The first flower visited by an insect will be self-pollinated as the visitor backs out of it. Should insect-visits fail, automatic self-pollination of unexploded flowers is possible, and may be effective under certain conditions (vide infra). BurkiU (Proc. Phil. Soc, Cambridge, viii, 1894) aptly describes the basal pro- cesses of alae and carina as two triggers, by which the flower is, so to speak, fired off. He states that the upper surfaces of the alae are beset with papillae, serving as foot-holds to insect visitors. There is also a marginal row of papillae on either side of the vexillum's inner surface, to which long-legged insects would appear to cling. The stigma remains unreceptive until its papillae have been subjected to friction. By covering a number of inflorescences with nets, in order to keep away insects, BurkiU was able to confirm the conclusion at which Urban had previously arrived (Verb. bot. Ver., Berlin, xv, 1873), that unex- 1^ I . \\ %.\ ^ th f \ni "^^^ ploded flowers do not set fruits, although their stigmas are sur- rounded by pollen. He succeeded, however, in inducing such flowers to fruit by (I) squeezing the stigma through the tip of the carina, (2) piercing the carina with a needle and scratching the stigma, (3) cutting off the tip of the carina and rubbing the stigma with a paint- brush. Visitors.—These are bees and Lepidoptera. The slender proboscis of the latter is undoubted- ly able to bring about explosion, providing it is thrust down to the nectar from the middle of the flower, while, on the other hand, explosion is not effected by insects that suck laterally, as the honey-bee, which inserts its proboscis into the base of the fl
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