ROSACEA E 



361 



anthers, so that at this stage cross-pollination must result from insect-visits. The 

 stamens now elongate, bringing the pollen-covered anthers to the level of the outer 

 stigmas, so that when the flower closes automatic self-pollination is readily effected. 



Insect visitors usually hang on to the flowers from below, by means of the 

 second and third legs, and thrust their heads and first legs into them. Some 

 humble bees, especially Bombus terrester Z., also steal nectar from the outside, 

 without rendering any service in return. The proboscis is inserted between the 

 calyx and petals. 



A. Schulz states that, besides hermaphrodite flowers, there are unisexual ones, 

 distributed androdioeciously or andromonoeciously. These male flowers are of the 

 same size as the ordinary kind. There is a group of vestigial carpels in the middle 

 of the stamens. Warnstorf also observed andromonoecism and androdioecism, the 

 male flowers, however, being much smaller than the others. He describes the pollen- 

 grains as being of a beautiful )'ellow colour, very irregular, roundish, tetrahedral 

 or ovoid, slightly tuberculated, up to 43 /a long and 25 /u. broad. Warnstorf also 

 states that the flowers are very frequently visited and robbed by humble-bees. 



Fig. 114. Ceum rivale, Z.. (from nature; enlarged). A. Flower (after removal ol the anterior 

 sepals and petals) in the first stage, with stigmas (s) mature, and anthers (a) still unripe. B. The same, 

 in the second stage, with stigmas still receptive, and anthers partly dehisced (a^), partly still unripe (a'). 



Visitors. — Herm. Muller (H. M.) in Westphalia, Loew (L.) in Brandenburg, 

 and myself (Kn.) in Schleswig-Holstein observed the following. — 



A. Coleoptera. Nilidulidae: I. Meligethes, freq., completely covered with 

 pollen (H. M., Kn.). B. Diptera. Syrphidae: 2. Eristalis nemorum Z., po-dvg. 

 (Kn.); 3. Rhingia rostrata Z., skg. and po-dvg. (H. M., Kn.). C. Hymenoptera. 

 Apidae: 4. Andrena helvola Z. 5, vainly seeking for nectar (H. M.); 5. Apis melli- 

 fica Z. 5, freq., skg. from the outside (H. M., L., Kn.); 6. Bombus agrorum F. 5, 

 skg. (H.' M., L., kn.); 7. B. confusus Schenck 5, do. (H. M.); 8. B. distinguendus 

 Mor. $, very occasionally, skg. (H. M.) ; 9. B. hortorum Z. ? and §, very common, 

 skg. (H. M.); 10. B. hypnorum Z. 5, skg. (H. M.); 11. B. lapidarius Z. 5, do. 

 (H. M., L., Kn.); 12. B. pratorum Z. 5, do., 5 also po-cllg. (H. M.); 13. B. scrim- 

 shiranu's K. 5 and $, skg. (H. M.); 14. B. muscorum F. 5, do. (H. M.); 15. B. 

 sylvamm Z. $, freq., skg. and po-cltg. (H. M.); 16. B. terrester Z. 5, skg. (H. M.). 



Herm. Muller saw 2 humble-bees in the Alps (' Alpenblumen,' p. 227). 



Gerstacker observed Osmia bicolor Schr. $, po-cltg., at Berlin. 



