214 ANGIOSPERMAE DICOTYLEDON ES 



nectar, secreted and sheltered by the hollowed sepals, is protected from rain. The 

 yellowish flowers smell strongly of honey, and are protandrous, as Hildebrand first 

 pointed out (op. cit.). The numerous stamens curve outwards, projecting beyond 

 sepals and petals. Insects settling upon the hanging blossoms can therefore only 

 find footing on the stamens and stigmas, or in the space between them. In the 

 younger flowers, therefore, they dust themselves with pollen, and transfer this to 

 the stigmas of the older flowers. Automatic self-pollination is scarcely possible, 

 for the stamens remain curved outwards to the end of anthesis. The flowers, how- 

 ever, are visited by so many insects that crossing is certain. Warnstorf (Verh. bot. 

 Ver., Berlin, xxxvii, 1895) says that the pollen-grains of T. platyphyllos are white, 

 tetrahedral, closely tuberculated, opaque, with three germinating processes in the 

 middle of the edges, and averaging 31 p in diameter. Jordan states that the exposed 

 nectar collects in two little pits on the bases of the sepals, and is accessible even 

 to very short-tongued insects. Besides the honey-bee which visits the flowers in 

 thousands, and collects nectar only, not pollen, other Apidae, as well as Syrphidae 

 and Muscidae, are very frequent visitors. 



Visitors. Herm. Miiller (H. M.) in Westphalia, and myself (Kn.) in Schleswig- 

 Holstein, have observed the following. 



A. Diptera. (a) Muscidae: 1. Lucilia cornicina F., skg. (H. M.); 2. Musca 

 domestica Z., do. (H. M., Kn.); 3. Sarcophaga carnaria Z., do. (H. M., Kn.). (b) 

 Syrphidae : 4. Eristalis arbustorum Z., skg. (H. M.) ; 5. E. nemorum L., do. (H. M., 

 Kn.); 6. E. sepulcralis Z., do. (H. M.); 7. E. tenax Z., do. (H. M., Kn.); 8. Helo- 

 philus floreus Z., very freq., skg. and po-dvg. (H. M.) ; 9. Volucella bombylans Z., 

 skg. (Kn.); 10. V. pellucens Z., do. (H. M.). (c) labanidae: n. Tabanus bovinus 

 Z., do. (H. M.). B. Hymenoptera. (a) Apidae: 12. Apis mellifica Z. , skg. 

 (H. M., Kn.); 13. Bombus agrorum F. 5, freq., skg. (H. M.) ; 14. B. lapidarius Z., 

 skg. (Kn.) ; 15. B. soroe'nsis F., var. proteus Gerst., do. (Kn.) ; 16. B. terrester Z., do. 

 (Kn.); 17. Prosopis, freq. (H. M.). (b) Sphegidae: 18. Oxybelus uniglumis Z., freq., 

 nect-lkg. (H. M.). 



Alfken saw the following at Bremen. 



A. Diptera. Empidae: 1. Empis tessellata F. B. Hymenoptera. (a) 

 Apidae: 2. Bombus agrorum F. ^ and j; 3. B. muscorum F. 5 and $>. (b) Vespidae: 

 4. Vespa crabro Z. tjj and $>. 



542. T. tomentosa Moench. (Kirchner, 'Flora v. Stuttgart,' p. 330.) -This 

 Hungarian species possesses bright yellow homogamous flowers, in which the stigma 

 projects beyond the anthers, so that cross-pollination is assured in the event of 

 insect-visits. 



543. T. sylvestris Desf. 



Visitors. MacLeod saw a humble-bee and 4 Diptera in the Pyrenees (Bot. 

 Jaarb. Dodonaea, Ghent, iii, 1891, p. 400). 



XXIII. ORDER L1NEAE DC. 



Flowers homogamous, with concealed nectar. Dimorphism frequent. 



Alefeld says that many European, Asiatic, and North African species are 

 dimorphous, while the Cape species, and those native to North and South America, 

 are monomorphous. 



