CRUCIFERAE 



99 



species. Kirchner states, however, that the protogyny is somewhat more pronounced. 

 The anthers which have a little red spot at the tip dehisce very soon after the 

 flower opens. The flowers are somewhat larger than in the last species, but owing to 

 the elongation of the axis of the inflorescence, are less crowded. 



Visitors. I observed the same as in the last species. 



Wustnei saw Andrena carbonaria L. in the island of Alsen. Alfken observed 

 lithe following on B. Napus and B. Rapa at Bremen. 



A. Diptera. Syrphidae: i . Orthoneura nobilis Fall. ; 2. Platycheirus albimanus 

 wF. ; 3. Syrphus venustus Mg., very freq. B. Hymenoptera. Apidae : 4. Andrena 



ilbicrus K. 5, freq.; 5. A. argentata Sm. $; 6. A. carbonaria L. 5 and J, infrequent; 

 I7. A. cineraria L. 5, infrequent; 8. A. cingulata F. 5, infrequent ; 9. A. flavipes Pz. 5, 



freq.; 10. A. fucata Sm. $>, infrequent; n. A. nigroaenea K. 5, not infrequent; 

 "12. A. parvula K. $>, very freq.; 13. A. propinqua Schenck <j> and S, very freq.; 

 W14. A. tibialis K. 5, infrequent; 15. Eriades florisomnis L. 5 and J, infrequent; 

 II16. Halictus calceatus Scop. $, very freq. ; 17. H. flavipes F. 5, freq. ; 18. H. leucopus 



K. 5, infrequent ; 19. H. nitidiusculus K. $, not infrequent ; 20. H. rubicundus Chr. 5, 



freq. ; 21. H. sexnotatulus Nyl. $>, infrequent; 22. Nomada bifida Ths. 5, infrequent ; 

 1 23. N. lineola Pz. 5, skg., infrequent ; 24. N. ruficornis L. van flava Pz. $, infrequent ; 

 1 25. Osmia rufa L. $> and J, freq. ; 26. Podalirius acervorum Z. $, infrequent ; 27. P. 



retusus L. 5 and J, freq. 



Schmiedeknecht noticed Osmia bicolor Schr. 5, in Thuringia. 



MacLeod in Flanders observed the following on B. napus and B. Rapa. 

 Apis, a humble-bee, 6 short-tongued bees, 4 hover-flies, 3 other Diptera, 2 Lepido- 

 ptera, and a beetle (Bot. Jaarb. Dodonaea, Ghent, vi, 1894, p. 205). 



De Vries saw the bee Andrena dorsata K. in the Netherlands. 



232. B. nigra Koch. (Kirchner, 'Flora v. Stuttgart,' p. 299; MacLeod, Bot. 

 Jaarb. Dodonaea, Ghent, vi, 1894, pp. 205-6; Knuth, 'Bl. u. Insekt. a. Helgoland,' 

 ' Bl. u. Insekt. a. d. nordfr. Ins.') The strong kumarin odour and the yellow colour of 

 the numerous flowers attract many insects wherever the plant is common, as for 

 instance on the high ground of Helgoland. The yellow sepals project obliquely ; 

 the petals are erect ; the diameter of the flower is 1 1-1 2 mm. As the long stamens 

 iare at the same level as and only about 1 mm. from the stigma, pollen can fall upon 

 it when the flowers are bent by the wind, thus effecting automatic self-pollination. 

 The long stamens are turned towards the two short ones, which being 2-3 mm. lower 

 than the stigma, can never effect self-pollination, but serve for cross-pollination. This 

 is brought about by numerous insects, which probe for the nectar secreted in the base 

 of the flower, soon getting dusted with pollen, that they afterwards brush off on the 

 stigma projecting from the middle of some other flower. There are four green 

 nectaries of about the same size, one on the inner side of each short stamen and one 

 on the outer side of each pair of long stamens. They secrete copiously. Kirchner 

 says that on different stocks the styles are of varying length, so that the stigma 

 may be either at the level of the short stamens or of the long ones. I have not 

 observed such variations in Helgoland. 



Visitors. I observed in Helgoland numerous po-dvg. flies and po-cltg. or 

 nectar skg. bees. 



A. Diptera. (a) Muscidae: 1. Calliphora erythrocephala, Mg., very freq.; 

 2. C. vomitoria L., freq.; 3. Coelopa frigida Fall., very freq.; 4. Cynomyia 

 mortuorum L. S, freq.; 5. Fucellia fucorum Fall., very freq.; 6. Lucilia caesar 



H 2 



