662 ANGIOSPERMAEDICOTYLEDONES 



florets are usually of a bright purple colour, and, according to Hermann Miiller, 

 from 60 to over 100 are found in one head. The capitulum is compressed below to 

 a diameter of 8-10 mm., but spreads out above to form a surface 20-30 mm. across. 

 The sterile ray-florets only serve to render the heads conspicuous, and are modified 

 into large outwardly directed funnels. The disk-florets are hermaphrodite; the 

 corolla-tube is 7-10 mm. and the bell 3-4^ mm. long. There are 5 linear 

 corolla-lobes, 5 mm. in length. The filaments are hairy and irritable; they 

 bend when touched by the proboscis of an insect visitor, pulling down the anther - 

 cylinder. The result is that the annular stylar brush sweeps out the pollen contained 

 in the cylinder. At a later stage the style grows out from this, and the papillose 

 inner surfaces of the stylar branches of the style separate to some extent. Automatic 

 self-pollination is therefore excluded, according to Hermann Miiller. ( Vide supra for 

 Kerner's view.) But self-pollination may be brought about by insects when the 

 stigmatic papillae are exposed, if the pollen has not been completely removed. 

 When visitors are numerous, however, no pollen is left on the head during the second 

 stage of anthesis, so that crossing is necessarily effected. Warnstorf describes the 

 pollen-grains as white in colour, ellipsoidal, furrowed, and covered with low spinose 

 tubercles, about 56^ long and 30 /a broad. 



Hermann Miiller also observed plants bearing male and female heads with enlarged 

 ray-florets, while MacLeod (in Belgium) saw some rayless female heads besides the 

 hermaphrodite ones, with neuter ray-florets. The male heads are of a paler colour ; 

 their ray-florets are greatly enlarged ; the nectary is vestigial, and the stylar branches 

 are permanently apposed. The florets of the female heads are darker and smaller, 

 with shrunken anthers devoid of pollen. 



Visitors. Herm. Miiller (H. M.) and Buddeberg (Budd.) give the following 

 list for Central Germany. 



A. Diptera. (a) Conopidae: 1. Conops flavipes Z., skg. (H. M.) ; 2. Physo- 

 cephala vittata F., do. (H. M.); 3. Sicus ferrugineus Z., do. (Budd.). (5) Empidae: 

 4. Empis livida Z., skg. (H. M., Budd.) ; 5. E. rustica F., do. (H. M.). (c) Syrphidae : 

 6. Eristalis intricarius Z., skg. (H. M.) ; 7. E. tenax Z., po-dvg., and inserting its long 

 proboscis into the bells of the individual florets (H. M.) ; 8. Helophilus pendulus Z., 

 skg. (H. M.); 9. Rhingia rostrata Z., do. (H. M.); 10. Syrphus balteatus Deg., 

 po-dvg. (Budd.). B. Hymenoptera. (a) Apidae: 11. Anthidium strigatum Pz., 

 po-cltg. (H. M., Thuringia); 12. Andrena pilipes F. 5, po-cltg. (H. M.); 13. Apis 

 mellifica Z. $, freq., skg. and po-cltg.; 14. Bombus agrorum F. 5, skg. (H. M.); 

 15. B. lapidariusZ. 5, do. (H. M.); 16. B. pratorumZ. J, do.(H. M.); 17. B. syl varum 

 Z. 5 and |jf, do. (H. M.); 18. Dasypoda hirtipes F. $, in large numbers, skg. (H. M.); 

 19. Halictus albipes F. J, skg. (H. M.) ; 20. H. cylindricus F. 5 and $, very common, 

 skg. and po-cltg. (H. M.) ; 21. H. interruptus Pz. $, skg. (H. M.); 22. H. leucozonius 

 Schr. 5 and $, skg. and po-cltg. (H. M.); 23. H. longulus Sm. $ and J (H. M.) ; 24. 

 H. lucidulus Schenck $, skg. and po-cltg. (H. M.); 25. H. maculatus Sm. % and $, do. 

 (H. M.) ; 26. H. malachurus K. 5, do. (Budd); 27. H. minutus K. S, skg. (H. M.) ; 

 28. H. nitidiusculus K. J and $>, po-cltg. and skg. (H. M.); 29. H. quadricinctus 

 F. j and 4, freq., skg. and po-cltg. (H. M., Budd.); 30. H. rubicundus Chr. 

 2 and $, skg. and po-cltg. (H. M.); 31. H. sexcinctus F. $, skg. (Budd.); 

 32. H. smeathmanellus K. $>, skg. and po-cltg. (H. M.); 33. H. tetrazonius Klg. 

 5 and J, skg. (Budd.); 34. H. villosulus K. 5, skg. and po-cltg. (Budd.); 35. H. 

 zonulus Sm. J, skg. (H. M.) ; 36. Megachile centuncularis Z. $ and $, po-cltg. and 

 skg. (H. M., Budd.); 37. M. lagopoda Z. $, po-cltg. (H. M., Thuringia); 38. Osmia 



