PAPAVERACEAE 65 



effect either kind of pollination. During dull weather the flowers remain closed for 

 a long time, in which case the anthers dehisce in the bud and effect self-pollination. 

 Warnstorf describes these flowers as varying from slightly protogynous to homo- 

 gamous, and from this to protandrous. The pollen-grains are of a beautiful yellow 

 colour, rounded, finely tuberculated, and measuring up to 37 /x in diameter. 



Visitors.— These are chiefly insects vainly seeking for nectar, and next to 

 them come pollen-collecting bees and pollen-devouring flies. The larger bees 

 (humble-bees and the honey-bee) alight as a rule on the middle of the flower, thus 

 effecting cross-pollination, while smaller forms (species of Halictus) usually settle 

 on the edges of the blossoms, and only occasionally touch the stigma, in which casi- 

 either kind of pollination is equally probable. Hover-flies behave in the same way. 



The following visitors have been determined by Hermann Muller (H, M.) in 

 Westphalia, and by myself (Kn.) in Schleswig-Holstein.— 



A. Coleoptera. (a) Chrysomelidae: i. Crvptocephalus sericeus Z., po-dvg. 

 (Kn.). {b) Nitidulidae : 2. Meligethes, po-dvg. (H.M.). B. Diptera. [a) Empidac: 

 3. Empis livida Z., vainly searching for nectar, or perhaps boring (H. M.). {V) Syr- 

 phidae: 4. tAscia podagrica F., po-dvg. (H. M.); 5. Eristalis arbustorum Z., po-dvg. 

 (H.M.); 6. E. nemorum Z,, po-dvp. (Kn.) ; 7. E. pertinax Scop., po-dvg. (Kn.) : 

 8. Helophilus pendulus Z., po-dvg. (Kn.) ; g. Melanoptoma mellina Z., po-dvg. (Kn'.") ; 

 10. Melithreptus taeniatus Mg., po-dva;. (Kn.) ; 11. Rhingia rostrata Z., first vainly 

 searching for nectar, then po-dvg. (H. M.^ ; 12. Syritta pipiens Z.. po-dv^. (H. M.^ ; 

 13. Syrphus balteatus Deg., po-dvg. (H. M.,, Kn.) ; 14. ?. ribesii Z., po-dvg. (H. 1\T., 

 Kn.). C. Hymenoptera. (a) Apidae: i.:;. Anthophora pilipes F. 5, po-cltg. (Kn.) ; 

 16. Apis mellifica Z. 5, po-cltg. (H. M., Kn.): 17. Bombus agrorum F. 5, po-cltg. 

 (H. M., Kn.); 18. B. horlorum Z. 5, po-cltg. (Kn.) ; 19. B. lapidarius Z. 5, po-chs. 

 (Kn.) ; 20. B. pratorum Z. $, po-cltg. (H. M.) ; 21. B. raiellusZ'. 5, po-cltg. (H. M.) ; 

 22. B. terrester Z., po-cltg. (Kn.). Herm. Muller noticed that humble-bees settle on 

 the middle of the flower, sweep pollen very rapidly from the anthers with the tarsal- 

 brushes of the first two pairs of legs, and immediately transfer it to the ' baskets ' of 

 the hind-legs, completing the operation in from two to three seconds, and then 

 at once flying away to another flower to treat it in the same fashion, thus effecting 

 cross-pollination. 23. Halictus cvlindricus F. 5 (H. M.) ; 24. H. sexnotatus A'', g 

 (H. M.) ; 25. H. sexstrigatus Scherick 5 (H. M.) ; 26. H. zonulus Sm. 5 (H. M.) ; these 

 four species of Halictus fly to the anthers to collect pollen, occasionally touching; 

 the stigma. 



Loew observed — in the Berlin Botanic Garden — a hover-fly, Syrphus balteatus 

 Deg; po-dvg.; Alfken — at Bremen — 3 po-cltg. Apidae, Bombus lucorum Z. 5, 

 Andrena nitida Foiirc. 5, and A. nigro-aenea K. 5, the last two flvintr laboriously 

 with disarranged wings, and carrying very heavy loads of pollen, destined to store 

 cells in the case of the last-named species ; Hoffer records from Steiermark, Bombus 

 agrorum F. 5. carrving huge loads of pollen, and Bombus terrester Z. 5 freq.; 

 MacLeod noted in Flanders, Apis, 3 humble-bees, 2 species of Halictus, 5 hover- 

 flies, and a Muscid (B. Jaarb. Dodonaea, Ghent, vi, 1894, pp. 186-7). 



42. Eschscholtzia Cham. 



Homogamous pollen flowers, usually yellow in colour. 



144. E. californica Cham. (F. Miiller, Bot. Ztg., Leipzig, xxvi, 1868 ; Darwin, 

 op. cit., xxvii, T869 ; Hildebrand, Jahrb.wiss. Bot., Leipzig, vii, 1869-70; Herm. Muller, 

 'Fertilisation,' pp. 94-5, 'Weit. Beob.,' L P- .323 ; Knuth, ' Blutenbiol. Herbstbeob.')— 

 The filiform stigmas are at first closely surrounded by the crowded stamens, but 



