298 BRITISH FLOWERING PLANTS chap. 



If any pollen is left some might easily fall on it, but, 

 according to Darwin, the flowers are not very suscep- 

 tible to their own pollen. They are principally visited 

 by bees, and Darwin says by more than in the case of 

 any other plant he knew. The plant is rough, with 

 stiif hairs on tubercles. It is not a native, but occurs 

 in waste ground near dwellings. 



Symphytum (Comfrey) 



Flowers homogamous. Corolla tubular, enlarged 

 above the middle. Nectar secreted by the base of the 

 ovary. According to Kerner, the flowers gradually bend 

 down, so that the stigma comes into the fall line of the 

 pollen. There are two British species — S. officinale, 

 with decurrent leaves ; S. tuberosum, with leaves not, or 

 only very slightly, decurrent. 



S. officinale. — The corolla is white or purple- violet. 

 The arrangement of the stamens resembles that of 

 Borage, but the flower-tube is longer — 14 mm. The 

 upper swollen part, however, occupies 6 mm., but a 

 proboscis 11 mm. in length is required to reach the 

 honey, because when the tube contracts the entrance is 

 still further protected by five triangular scales and by 

 the stamens. Bombus terrestris and other humble 

 bees, however, often bite through the corolla, and thus 

 rob the flower of its honey. The leaves are rough, with 

 short scattered hairs, and longer ones on the ribs. 



S. tuberosum is less roughly hairy than the preceding. 

 It is not found in the South of England. 



ASPERUGO 



The calyx enlarges after the flower fades, and becomes 

 flattened and veined. The flowers are homogamous, 

 with nectar secreted by the base of the ovary. 



A. procumbens. — The flowers are small and blue. 

 The plant is rough, with • hooked hairs turned down- 

 wards. It is not common in Britain, but is occasionally 

 found in waste places. 



