ROSACEAE 347 



826. P. spinosa L. (Herm. Miiller, 'Fertilisation/ p. 221, ' Weit. Beob.,' II, 

 p. 244; MacLeod, Bot. Jaarb. Dodonaea, Ghent, vi, 1894, pp. 323-4; Knuth, 

 ' Bloemenbiol. Bijdragen.') In the principal variety of this species the fragrant white 

 flowers appear before the leaves. They so abundantly bedeck the numerous dark 

 branches of the thorny shrub that it can be seen from a distance, so that at the 

 time of anthesis the blackthorn is the most conspicuous member of our flora. 

 The blossoms are consequently visited by numerous insects, which either seek 

 out the nectar secreted abundantly in the base of the receptacle or else collect 

 pollen. They are protogynous : when the flower-buds expand the anthers are 

 still closed, while the style projects a few millimetres beyond the crowded central 

 mass of stamens, and as the stigma is already receptive, cross-pollination must be 

 effected by insects that have previously visited an older flower in the male stage. 

 The stamens subsequently elongate, spread themselves out, and open their anthers. 

 The style also becomes longer, so that it projects somewhat beyond the shorter 

 stamens. The stigma remains receptive, so that, should insect-visits fail, automatic 

 self-pollination can take place. 



Visitors. Hermann Miiller (H. M.) and myself (Kn.) have observed the 

 following. 



A. Coleoptera. Nitidulidae : 1. Meligethes, nect-skg. (H. M., Kn.). B. Di~ 

 ptera. (a) Bibionidae : 2. Bibio marci Z., nect-lkg. (H. M.). {b) Evipidae : 3. Empis 

 rustica Fall, skg. (H. M.). (c) Muscidae: 4. Species of Anthomyia, skg. (H. M.) ; 5. 

 Chlorops sp., do. (H. M.) ; 6. Musca domestica Z., do. (Kn.) ; 7. Scatophaga merdaria 

 F, do. (H.M.); 8. S. stercoraria Z., do. (H. M., Kn.); 9. Sepsis, freq., skg. (H.M.). 

 (d) Syrphidae: 10. Eristalis arbustorum Z., skg. and po-dvg. (H. M.) ; 11. E. intri- 

 carius Z., do. (H. M.); 12. E. nemorum Z., do. (H. M.) ; 13. E. tenax Z., do (H. M., 

 Kn.); 14. Rhingia rostrata Z., skg. (Kn.). C. Hymenoptera. (a) Apidae: 15. 

 Andrena albicans Mull. 9 and $, skg. and po-cltg. (H. M., Kn.) ; 16. A. atriceps K. 9. 

 and J, skg. (H.M.); 17. A. dorsata K. 9, po-cltg. (H. M.); 18. A. fasciata Wesm. 5, 

 skg. (H. M.); 19. A. fulva Schrank 9, skg. and po-cltg. (H. M.) ; 20. A. fulvicrus K. 

 % and $, skg. (H. M.); 21. A. gwynana K. 9, skg. and po-cltg. (H. M.); 22. A. 

 parvula K. 9, do. (H. M., Kn.) ; 23. A. eximia Sm. 9., do. (H. M.); 24. A. schran- 

 kella Nyl. 9, po-cltg. (H. M.) ; 25. Apis mellifica Z. , skg. and po-cltg. (H. M., Kn.); 

 26. Bombus lapidarius Z. J, skg. (H. M.); 27. Halictus albipes F. 9, freq., skg. and 

 po-cltg. (H.M.); 28. H. cylindricus F. 9, do. (H. M.); 29. Nomada succincta Pz. S, 

 skg. (H. M.); 30. Osmia rufa Z. 5, do. (H. M.). (6) Tenthredinidae : 31. Dolerus 

 gonager Kl, skg. (H. M.). D. Lepidoptera. Rhopalocera: 32. Vanessa io Z., 

 persistently skg. (H. M.). 



Alfken noticed the following at Bremen. 



A. Diptera. (a) Bombyliidae: 1. Bombylius major Z., freq., skg. (b) Muscidae: 

 %, Sarcophaga carnaria Z., skg. (c) Syrphidae: 3. Eristalis arbustorum Z., very 

 common, skg. and po-dvg. ; 4. E. intricarius Z., do. ; 5. Helophilus pendulus Z., do.; 

 6. Platycheirus albimanus F. ; 7. Syritta pipiens Z. B. Hymenoptera. (a) Apidae: 

 8. Andrena albicans Mull. 9 and $; 9. A. albicrus K. 9 and 5; 10. A. extricata 

 Sm. 9; 11. A. flavipes Pz. 9; 12. A. helvola Z. J; 13. A. nitida Fourc. 9; 14. A. 

 Marians K. 9 and J ; 15. Apis mellifica Z. 5, very common, skg. ; 16. Halictus flavipes 

 F. 9; 17. H. morio F. 9; 18. H. nitidiusculus K. 9; 19. Nomada alternata K. 5; 

 20. N. lineola Pz. $, skg.; 21. N. succincta Pz. S; 22. Osmia rufa Z. J. (b) Ten- 

 thredinidae: 23. Hoplocampa ferruginea F. ; 24. H. rutilicornis Klg. 



Gerstacker records a bee, Osmia aurulenta Pz., freq., for Berlin. 



