684 ANGIOSPERMAE—DICOTYLEDONES 



Hermann Miiller states that a head consists of 100-200 florets with corolla-tubes 

 3-7 mm. and ligules 7-15 mm. in length. The anther- cylinder projects 2^5 mm. 

 from the corolla-tube, and the style extends 3-5 mm. further. In the second stage of 

 anthesis, the stylar branches, which are 1^2 mm. long, bend outwards and roll 

 back so far as to form a spiral of i^ turns. If, therefore, the pollen has not all 

 been removed by insect visitors, automatic self-pollination necessarily takes place. 

 According to Kemer, automatic geitonogamy also takes place, the stylar branches 

 of the outer florets diverging and rolling back so as to come into contact with 

 the pollen of the inner ones. Hansgirg also observed pseudo-cleistogamous florets. 

 Warnstorf describes the pollen-grains as golden-yellow in colour, polyhedral, spinose, 

 about 37 /i in diameter. 



Visitors. — Alfken observed the following at Bremen. — 



A. Diptera. (a) Bibionidae : r. Bibio marci L., not infrequent. (3) Empidae: 

 2. Empis ciliata Z., freq. ; 3. E. opaca F., excessively freq., skg. (c) Syrphidae: 



4. Eristalis arbustorum L., freq., skg.; 5. E. intricarius L., do.; 6. E. pertinax Scop., 

 do.; 7. E. sepulcralis Z., not infrequent, skg.; 8. E. tenax Z., very common, skg.; 

 9. Helophilus pendulusZ.,do. ; 10. Leucozona lucorum Z., rare, skg. ; 11. Sericomyia 

 borealis Fall., freq., skg.; 12. Spilomyia vespiformis Z., very rare; 13. Syrphus 

 tricinctus Fall., skg. ; 14. S. venustus Mg., very common, skg. B. Hymenoptera. 

 (a) Apidae: 15. Andrena albicans Miill., very common, 5 skg. and po-cltg., S skg. 

 This is the commonest pollinator: with obvious satisfaction it lies on its side and 

 probes the inflorescence. 16. A. albicrus K. 5 and S, not infrequent; 17. A. apicata 

 Sm. 5 and S, rare, it chiefly visits willows; 18. A. argentata Sm. 5, rare; 19. A. 

 carbonaria Z., 5 and S, do. ; 20. A. chrysosceles K. 5 and $, do. ; 21. A. cineraria 

 Z. 5, freq., skg. and po-cltg., t> very common, skg. ; 22. A. cingulata F. 5 and S, very 

 rare ; 23. A. convexiuscula K. $ and S, rare ; 24. A. dorsata K. S, once ; 25. A. extri- 

 cata Sm. $ not infrequent, skg. and po-cltg., 5 very common, skg. ; 26. A. flavipes Pz. 

 5 extremely freq., skg. and po-cltg., t do., skg.; 27. A. fucata Sm. 5, very rare; 

 28. A. fulvaga Chr. S; 29. A. gwynana K. 5 not infrequent, skg. and po-cltg., 5 

 not infrequent, skg. ; 30. A. helvola Z. 5 and 5, very rare ; 31. A. humilis Imh. 5 and $, 

 mostly stylopized individuals; 32. A. labialis K. j and $, rare; 33. A. labiata Schenck 



5, very rare, skg. and po-cltg.; 34. A. morawitzi Ths. 5 and J, not infrequent; 35. A. 

 nigroaenea K. 5 very common, skg. and po-cltg., S very common, skg, ; 36. A. nitida 

 Fourcr. 5 very common, skg. and po-cltg., J very common, skg.; 37. A. ovina Klg. 

 5 infrequent, skg. and po-cltg., S rare, skg. ; 38. A. parvula K. 5 very common, skg. 

 and po-cltg., S not frequent, skg. ; 39. A. praecox Scop, j, not freq., skg. and po-cltg., 

 chiefly visits willows, S rare; 40. A. propinqua Schenck; 41. A. proximal. J and $, 

 rare; 42. A. rufitarsis Zelt. 5 freq., skg. and po-cltg., 5 very rare; 43. A. thoracica F. 

 5 rare, skg. and po-cltg., 5 rare, skg. ; 44. A. tibialis K., rare, 5 skg. and po-cltg., $ 

 skg. ; 45. A. trimmerana K., do., 5 do., S do. ; 46. A. varians K. 5 and S, rare ; 

 47. Bombus agrorum F. 5, not infreq., skg. and po-cltg.; 48. B. arenicola Ths. 5, 

 rare ; 49. B. derhamellus K. ?, freq., skg. and po-cltg. ; 50. B. distinguendus Mor. j, 

 not infreq., skg. and po-cltg.; 51. B. hortorum Z. 5 rare, S rare, skg. in plants 

 flowering in autumn; 52. B. jonellus K. 5, rare, skg. and po-cltg., a characteristic 

 visitor of willows; 53. B. lapidarius Z. 5, very common, skg. and po-cltg.; 54. B. 

 lucorum Z. 5, do.; 55. B. muscorum F. 5 and 5, not infreq., skg. and po-cltg.; 

 56. B. pratorum Z. 5, skg. ; 57. B. ruderatus F. 5, rare, skg. and po-cltg. ; 58. B. 

 sylvarum Z. 5, not infreq., skg. and po-cltg.; 59. B. terrester Z., very common, skg. 

 and po-cltg. ; 60. Collates cunicularius Z. 5, rare, po-cltg. ; 61. Eriades florisomnisZ. 

 5 and J; 62. Eucera difficilis {Duf.) Per. J ; 63. Halictus calceatus Scop., and var. 

 elegans Lep. 5, rare, skg. and po-cltg. ; 64. H. flavipes F. 5, freq., skg. and po-cltg. ; 

 65. H. levis K. 5, not infrequent, skg. and po-cltg.; 66. H. malachurus K., very rare ; 



