68 



ANGIOSPERMAE—DICOTYLEDONES 



at the only two places where there are openings into the interior of the flower. 

 The parts of the filaments projecting from the flower — together with the anthers — he 

 close together, surrounding the stiff style with its stigma, and they themselves are 

 covered with a hood formed by the fusion of the tips of the two inner petals. 



Some considerable time before the flower opens the anthers dehisce, discharging 

 their pollen upon the large lobed stigma — which is already mature — and there the 

 pollen lies surrounded by the hood. Automatic self-pollination would therefore be 

 inevitable, and the pollen could never escape from its close envelope, were not 

 crossing effected by insects, which in this case are exclusively bees. When a bee 

 hangs on to the flower to suck nectar, it must push aside the hood and the flexible 

 stamens this encloses with the under-side of its body, and — with the hairs on its 

 ventral surface — sweep off the pollen from- the stigma, which owing to the rigidity 

 of the style is not deflected. As soon as the bee leaves, the hood returns to its 

 former position, and again ensheaths the anthers and stigma. There being two 



12 3 4 



Fig. 23. /J/i:/v/r« .s/'«i'a«/7«, ifSC. (after Hlldebrand). (1) Flower, natural size. (2) The same after 

 removal of half an outer petal : the hood is pressed aside : the dotted line beffinning at e, indicates the 

 path of the insect's probo=icis. {3) The sexual organs of a bud. (4) The pistil and the two middle stamens 

 of a bud before dehiscence of the anthers. 



nectaries, these events happen twice during a visit to each blossom. In younger 

 flowers therefore the pollen on the stigma is removed by the bee, and carried to 

 the stigma of an older flower, which has already been robbed of its own pollen. 



Visitors. — Since the curved channels of Diclytra spectabilis are 18-20 mm. 

 long, there are only two of our native bees which can reach the nectar in the 

 legitimate way, i.e. Bombus hortorum L. 5 (proboscis 20-21 mm. long), and 

 Anthophora pilipes F. 5 (proboscis 19-20 mm.). These two bees are in fact the 

 normal visitors and pollinators of this species. Hermann Muller observed both of 

 them sucking the flowers in Westphalia, and I myself saw B. hortorum doing so 

 in the Kiel Botanic Garden. Bees with a shorter proboscis steal the nectar by 

 biting tlirough the flower. Bombus terrester L. 5 — the proboscis of which is 

 7-9 mm. long — climbs to the upper side of the flower and bites through the petals 

 in the neighbourhood of the nectaries, afterwards extracting the nectar through 

 the hole. Hermann Miiller also observed B. pratorum /.. 5 (length of proboscis 

 11-12 inni.\ and L\ rajellus K. 5 (12-13 mm.), behaving in the same way, while 



