BORAGINEAE 



131 



neighbouring anther. The anthers thus collectively make up a pyramid closed 

 all round, with its apex directed downwards, and its axis formed by the style. It 

 becomes filled with the white powdery pollen when this is dehisced. 



As the corolla-lobes converge, an insect visitor (bee) inserts its proboscis into 

 one of the clefts between them, causing two stamens to become to some extent 

 separated. The anther pyramid is thus opened, and some of the dry powdery pollen 

 falls upon the under-side of the bee's head. As the stigma projects from the flower 

 it is first touched by the bee or humble-bee paying the visit, and pollen brought from 

 other flowers will be transferred to it. Crossing by insect-visits is thus ensured, and 

 the form of the inflorescence favours the transfer of pollen from one stock or at any 

 rate one branch to another. As anthesis progresses an inflorescence continues to 



A. 



Fig. 374. 0>'/M a///a, A'y. (after Herm. Mailer). A. Flower soon after opening. B. Do., 

 partly dissected from the side. C. Do., more strongly magnified. D. Completely expanded flower. 



(^, B, D X 4; C X 7.) a, a', a", regions of anthers ; co, corolla ; Jt, filament ; ^r, style ; , nectary ; 



ov, ovary; *, sepal ; st, stigma. 



elongate, and that part of it bearing fertilized flowers is directed obliquely upwards, 

 while the part bearing unvisited flowers and buds is curved down and rolled inwards. 

 It follows that old flowers in which the corolla is about to fall are feither directed 

 obliquely upwards to a slight extent or are placed horizontally, while younger ones 

 are directed obliquely or vertically downwards. The buds are on the rolled-up part 

 of the inflorescence. Humble-bees only cling to flowers facing obliquely or directly 

 downwards, the former being pulled into a vertical position by their weight. The 

 honey-bee only visits flowers directed vertically downwards. All visitors therefore 

 hang on to the bell-shaped corolla from below, and after a visit have to take wing 

 in order to reach another blossom. Their flight is always to another branch or 

 another stock ; at least Hermann MuUer never saw two flowers on the same 

 inflorescence visited in succession. 



K 2 



