II GENTIANACE^ 287 



corolla -tube is 25-30 mm. long, and 8-10 wide at 

 the mouth. Beneath the middle the tube suddenly 

 narrows, as the filaments of the stamens are soldered 

 to the corolla. To this point a bee can enter, and 

 touches with its head the pollen in young flowers, the 

 stigma in older ones. In this stage the stigma projects 

 above the anthers. Gradually, however, the tube 

 elongates, and brings the anthers to the level of the 

 stigma, so that in the absence of insect visits the flower 

 fertilises itself 



G. verna. — This species is fertilised principally by 

 butterflies. 



G. nivalis. — This species appears to be generally self- 

 fertilised. The flowers open and close rapidly — occa- 

 sionally, according to Kerner, several times in an hour. 



G. Amarella. — The flower - tube is 16-18 mm. in 

 length, but is 6 mm. wide, so that humble bees, by 

 which the flowers are principally visited; can push their 

 heads some 6 mm. down. At the entrance to the tube 

 are a number of hairs, which exclude unwelcome visitors, 

 especially flies, and, in combination with the contraction 

 of the flower, also serve to exclude rain. The anthers 

 open upwards and at the same time as the flower. The 

 two stigmas project somewhat farther, so that an 

 approaching insect must almost inevitably, in the first 

 instance, touch the stigma, and then dust itself with 

 pollen. 



G. campestris. — This species differs from the preceding 

 in having 4 sepals and 4 corolla -lobes. Two of the 

 sepals are wider than, and overlap the others. In some 

 districts it is said to be slightly protogynous, in others 

 protandrous. It appears also to differ in these respects 

 somewhat according to the season. In bad weather the 

 flowers are said to be cleistogamous. In Norway the 

 stigmas are at the same level as the anthers, or even 

 lower ; in the Alps, according to H. Miiller, they 

 project beyond the anthers, but finally bend over to 

 them and so fertilise themselves. They are visited by 

 humble bees and butterflies. An interesting point 



