12 2 Flowers and their Unbidden Guests. 



aWy found full of nectar so long as the flower is in 

 blossom. As the bell-shaped flower is 11-16 mm. 

 wide at the mouth, and as the anthers and stigma 

 are closely apposed to the upper wall of the corolla, 

 insects of aU varieties of size, with bodies of from 1-10 

 mm. in thickness, can make their entrance, and, for 

 all that has yet been mentioned, might carry off the 

 nectar from the above-described space without neces- 

 sarily touching the stigma and anthers ; but the nectar 

 is admirably protected against all such guests by 

 means of the fifth and uppermost stamen, which is 

 inserted upon the corolla about 6-7 mm. from the 

 bottom. This is converted into a "drop-bar," and 

 has its thickened and dilated base placed imme- 

 diately in front of the nectar-cavity, covering the 

 opening so completely that only a small fissure, scarcely 

 1 mm. in width, is left open on either side. This bar 

 runs obliquely across the flower, crossing therefore the 

 base of the other filaments and the style, and fixes 

 its free end, which is thickened but forms no pollen, 

 against the lower wall of the coroUa, like a buttress. 

 By this arrangement insects of sufficient size to be 

 brought, when visiting the flower, into due contact with 

 stigma and pollen are allowed to get at the nectar, 

 inasmuch as they can insert their trunk into the narrow 

 orifices on either side of the bar, while smaller and 

 therefore unwelcome visitors are completely shut out. 

 In many cases the ovary and the filaments, which 



