. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. GENTIANEAE 107 The anthers dehisce when the flower opens, their pollen-covered surfaces being directed upwards, so that if the head of a humble-bee is thrust into the corolla-tube it must touch them. The two stigmas simultaneously diverge, and as they project beyond the anthers cross-pollination is favoured, though autogamy is not excluded. In plants from the Dovrefjeld and Nordland, according to Lindman and Warming respectively, automatic self-pollination i
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. GENTIANEAE 107 The anthers dehisce when the flower opens, their pollen-covered surfaces being directed upwards, so that if the head of a humble-bee is thrust into the corolla-tube it must touch them. The two stigmas simultaneously diverge, and as they project beyond the anthers cross-pollination is favoured, though autogamy is not excluded. In plants from the Dovrefjeld and Nordland, according to Lindman and Warming respectively, automatic self-pollination is easily possible, for the anthers generally touch the stigma. Wamstorf describes the pollen-grains as whitish in colour, ellipsoidal, densely papillose, about 56 ju long and 44 /x broad. Visitors.—Herm. Miiller observed a humble-bee (Bombus sylvarum Z., with a proboscis of 12-14 mm.), skg. 1916. G. germanica Willd. (Ricca, Atti See. ital. sc. nat., Milano, xiii, 1870; Schulz, 'Beitrage'; Kerner, 'Nat. Hist. PI.,'Eng. Ed. i, II, pp. 302, 311.)—The large flowers of this species attain an average length of 28-32 mm., and are violet in colour, often with a whitish tube ; rarely pure white, and still more rarely yellow. They are heterostylous humble- bee Lepidopterid flowers, de- scribed by Schulz as feebly or strongly protandrous, by Kerner as protogynous. The nectaries are situated as in G. Amarella. Schulz states that the anthers are at first directed inwards, but gradually twist themselves round till they face outwards. In the homogamous or feebly protandrous flowers automatic self-pollination is possible, owing to the stigma and anthers being at the same level, but the out- wardly directed position of the latter renders it difficult. The flowers are homogamous in the Alps, but the stigma is at a higher level than the anthers, so that autogamy is impossible. Kerner describes the Alpine sub-species G. rhaetica Kerner as being hetero- stylous and protogynous. Visitors.— Ric
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