. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. SCROPHULARINEAE 167 this species the corolla is of a pale green colour, but the inner surface of the upper lip is brown and serves as a nectar-guide. The flower is so placed that the entrance of rain-drops is prevented. It is about 5 mm. in diameter. Insect visitors, particularly wasps, touch the stigma from below during the first stage of anthesis, and the anthers during the second. The posterior fifth stamen has become unnecessary, and is modified into a s
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. SCROPHULARINEAE 167 this species the corolla is of a pale green colour, but the inner surface of the upper lip is brown and serves as a nectar-guide. The flower is so placed that the entrance of rain-drops is prevented. It is about 5 mm. in diameter. Insect visitors, particularly wasps, touch the stigma from below during the first stage of anthesis, and the anthers during the second. The posterior fifth stamen has become unnecessary, and is modified into a small black leaflet on the upper wall of the corolla. Visitors are thus enabled to force their way into the flowers exactly in the middle line. They hold on to the outside of the corolla with all six legs, and push their heads into the entrance of the flower, pollinating those in the first stage, and dusting themselves with pollen in those in the second stage. It follows that when a number of flowers are visited in succession crossing will always take Fig. 286. Scrophularia nodosa^ L. (after Herm. Miiller). (i) Flower in the first (female) stage, seen directly from the front (x 7). (2) Do., from below ( x 3^). (3) Older flower, pollinating itself, seen from the side. (4-7) Stages in the reversion of the fifth stamen to the original leaf-like form (read from 7 to 4) (X 12). fl, calyx-lobes; b^ ; j, stamens; d^ modified fifth stamen; d, ovary; £, style; yj stigma; g, nectary ; A, drops of nectar ; /, black leaf-like part of fifth stamen ; k^ anthers. The first (female) stage of anthesis lasts for two days. The anthers are at this time unripe, and situated in the base of the flower on the bent filaments, while the style protrudes to some extent from the corolla and its receptive stigma is directed somewhat upwards. When the second (male) stage of anthesis begins, the filaments straighten and the pollinated stigma withers and bends down over the lower lip, its
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