BORAGINEAE 



133 



smaller bee at least comes into contact with the anther of the short stamen situated 

 in the entrance of the flower. The style runs between the stamens, and its end 

 divides into two short stigmatic branches. When the flower opens it is so short as 

 scarcely to reach the entrance, and is quite straight with its branches closely apposed. 

 In the course of anthesis it elongates till it projects ro mm. beyond the entrance of 

 the flower, and bends slightly upwards, while its branches diverge. At this stage the 

 style projects further and is bent more strongly upwards than any other part of the 

 alighting platform, so that neither large nor small insects can settle without bringing 

 their ventral surface into contact with one of the stigmatic branches. The cross- 

 pollination brought about in this way is ensured by the projection of the stigma, even 

 if at the time when it matures some pollen remains clinging to the anthers. Jordan 

 points out that it is sometimes effected by insects as they settle, and sometimes as 

 they withdraw and fly away. Schulz observed homogamy in rare cases. 



Hermaphrodite flowers are not the only kind found in this species, for stocks 

 very infrequently occur which bear female ones. In these the corolla is much 

 smaller and the style shorter, while the stamens are short and only produce abortive 

 pollen-grains. Between herma- 

 phrodite and female flowers there 

 are also transitional stages, in which 

 one, two, or three stamens are fully 

 developed and the remainder re- 

 duced. Schulz states that female 

 stocks are very widely distributed, 

 and sometimes as many as three- 

 quarters of the plants in a particular 

 locality are of this kind. He even 

 found places here and there, e.g. at 

 CoUeda, where nothing but female 

 stocks were to be seen. The size 

 of the female flowers varies con- 

 siderably, the corolla being 11-14 

 mm. long in the larger ones, and 

 only 7-9 mm. in the small ones. 

 Schulz often found the female 



stocks to be remarkably vigorous. He explains the development of female flowers 

 as due to the excessive strain on the supply of food resulting from the production of 

 infioreficences with a very large number of flowers. 



Visitors. Herm. Miiller (H. M.) for Westphalia and Thuringia (T.) and 

 Buddeberg (Budd.) for Nassau give the following list. 



A. Coleoptera. Oedemeridae : i. Oedemera virescens L., searching for nectar 

 (H. M.). B. Diptera. (a) Conopidae : 2. Physocephala rufipes F., skg. (H. M.) ; 

 3. P. vittata F., do. (H. M.) ; 4. Sicus ferrugineus Z., do. (Budd.). {b) Syrphidae : 

 5. Helophilus trivittatus F., po-dvg. (H. M.) ; 6. Melanostoma ambigua Fall, do. 

 (H. M.) ; 7. Microdon devius Z., do. (Budd.) ; 8. Rhingia rostrata Z., skg. (H. M.) ; 

 9. Syrphus arcuatus Fall,, po-dvg. (H. M.) ; 10. S. pyrastri Z., do. (H. M.). 

 C. Hymenoptera. (a) Aptdae: 11. Andrena albicrus K. J, skg. (H. M.); 12. A, 



Fig. 275. Echium vtdgare^ L. (after Herm. Miiller). 

 (i) An older flower, seen from the side (its actual position is 

 horizontal). (2) Basal transverse section of a flower, d/, corolla; 

 gy style ; A, nectar-passages ; k^ sepals ; , stigma ; st, stamens. 



