113 



is excreted by the yellow disc at the base of the ovary 

 and collects in the corolla tube. The flowers are much 

 \isited by bees and a bee alighting on the landing-stage 

 and wishing to get at the nectar has to pass forward under the 

 hooded upper lip of the corolla and it then finds the entrance 

 into the nectar-containing tube effectually blocked by an in- 

 genious piece of mechanism consisting of the two stamens which 

 is shown in Fig. 1, dissected from the flower. Each stamen is 

 attached to the corolla by a short filament on which the long 

 connective swings like a lever on its fulcrum. The upper longer 

 arm of the connective is slender and, together with the pollen- 

 bearing anther-lobe which it carries at its apex, is concealed in 

 the hooded upper corolla lip. The lower thickened connective 

 arm is joined to that of the other stamen which is placed side by 

 side with it in the flower, the metamorphosed lower anther- 

 lobes borne at their extremities coalescing to form a little pouch- 

 like structure which effectually blocks the entrance to the corolla- 

 tube, like a trap-door. See Fig. 2. The anthers dehisce by a 

 longitudinal slit which directly faces the landing 'stage. A bee 

 wishing to get at the nectar and pushing against the obstructing 

 door will move the latter upwards and backwards, the path to 

 the nectar thus being opened, while the upper connective arms 

 descend towards the landing stage and bring their pollen-covered 

 anthers down on the bee's back. See Fig. 3. So soon as the 

 bee withdraws, the stamens swing back into their former posi- 

 tion. The flowers of this plant are protandrous, i.e. the anthers 

 mature and begin to shed their pollen before the stigma is 

 ready for pollination." In a young flower the stigma occupies 

 the position shown in Fig. 4 (a), the stigmatic surfaces being close 

 together and well out of the way of an insect entering the flower. 

 As the flower gets older the style becomes depressed towards 

 the landing stage while the stigmatic lobes separate and become 

 recurved, Fig. 4 (6). A bee, before it can enter the flower at all, 

 must first bring its back, which has probably been dusted with 

 the pollen of a separate younger flower, in contact with the 

 stigmatic surface and cross-fertilisation is thus effected. 



102. In the case of Berberis Fertilisation 



Lycium, if we look at a flower-bud we find the stamens stand- of Flowers of 

 ing erect in the centre of the flower with their anthers close to 

 the stigma, but the anther-valves are then unopened as shown in 

 Fig. 5 (a), Plate XIV. As the flower expands and the petals 

 open out the stamens are bent back with them, the back of the 

 filaments being closely adpressed to the upper surface of the 

 petals. As the flower opens, also, the anthers dehisce. During 



