THE AXGIOSPERMAE 



1323 



The case of the Red Clover is so important that we shall describe the 

 pollination mechanism, though to a large extent it resembles the White 

 Clover already referred to. The flowers of TrifoUum pratetise (Fig. 1238) are 

 produced in racemose heads similar in shape to those of T. repens, but con- 

 siderably larger. The calyx is short, with five pointed sepals, fused basally 

 into a tube. The corolla consists of five petals, the vexillum being rather 



Fig. 1238. — Trifoliinn pratense. A, Flowering shoot. B, Flower after 

 pollination with depressed carina. C, Young flower showing vexil- 

 lum, alae and carina. D, Flower from side showing protruding 

 carina. E, Androecium showing single, free, posterior stamen. The 

 drawing is reversed. 



elongated and oval in shape. The alae are shorter than the vexillum and are 

 enclosed by it, while the carina is shorter than the alae and the two petals 

 which form it are fused marginally together. The basal parts of all five 

 petals are united to form a tube up to 10 mm. long. The stamens are diadel- 

 phous, nine of them being fused to one another and also to the corolla tube. 

 The upper, free stamen lies to one side of the flower and the opening it 

 leaves in the staminal tube forms a passage to the nectar, which is secreted 

 in the base of the corolla tube. Both the stamens and the stigma are en- 

 closed in the carina, where they are completely protected. When a Humble 

 Bee visits the flower it settles on the alae, which are united to the carina, 

 and the whole is depressed. This liberates the stigma, the tip of which 

 comes into contact with the underside of the insect. Meanwhile the bee 

 thrusts its proboscis into the flower and the anthers, which dehisce introrsely, 



