RANUNCULACEAE 3 



pollen-seeking bees. TroUius — a yellow flower with concealed nectar — receives 

 visits from Hymenoptera, Diptera, and Coleoptera, in about equal numbers, while 

 the violet Pulsatilla is pollinated almost exclusively by bees. Aquilegia, Delphinium, 

 and Aconitum, are characteristic humble-bee flowers; Nigella and Atragene are 

 equally characteristic bee flowers. 



I. Clematis L. 



IMostly pollen flowers with petaloid sepals, by which conspicuousness is secured. 



1. C. Vitalba L. (Herm. MuUer, ' Weit. Beob.,' I, p. 312 ; Schulz, 'Beitrage,' 



1, p. I ; Kirchner, 'Flora v. Stuttgart,' p. 258; Loew, ' Blutenbiol. Floristik,' 

 p. 175; Kerner, 'Nat. Hist. PI.,' Eng. Ed. i, II; Knuth, ' Bloemenbiol. Bijdragen,' 

 ' Blutenbiol. Notizen.') — Protogynous pollen flowers. The flowers are arranged in 

 dense cymes, carried high into the air by the climbing stem, so that the white 

 reflexed sepals, and the white stamens, make the plant conspicuous from a distance. 

 The hawthorn-like odour of the flowers (due to trimethylamine) serves as a further 

 means of attraction. The flowers are slightly protogynous (according to Schulz 

 occasional ones may be homogamous), and at the time of flowering the numerous 

 €rect undehisced stamens are rather lower than the stigmas, which are already 

 mature. The filaments now elongate, and bend outwards as the anthers dehisce. 

 Since the outer stamens are the first to ripen, self-pollination is at first rendered 

 •difficult. But as the stigmas continue receptive till the innermost stamens are ripe, 

 it becomes easy in the final stage of flowering. 



The visitors and pollinators are pollen-collecting bees and pollen-devouring 

 flies. These necessarily effect cross-pollination when they pass from one blossom 

 to another, alighting in the middle of the flower upon the rather prominent stigmas. 

 It is very difficult to observe their actions because of the height of the plant. 



Visitors. — The following have been observed by Buddeberg (Budd.) in Nassau, 

 by Hermann Muller (H. M.) in Westphaha, and by myself (Kn.) in Holstein. — 

 A. Diptera. (a) Muscidae: i. Musca domestica Z. (Kn.) ; 2. Sarcophaga carnaria 

 Z. (Kn.); 3. Scatophaga stercoraria Z. (Kn.) ; all po-dvg. (U) Syrphidae : 4. Eristalis 

 nemorum Z. (Kn.) ; 5. E. tenax Z. (Kn.) ; 6. Rhingia rostrata Z. (Kn.) ; 7. Syrphus 

 balteatus Z^^"^. $ (Kn.); 8. S. ribesii Z. 5 (Kn.) ; all po-dvg. B. Hymenoptera. 

 (a) Apidae: 9. Apis mellifica L. (Kn., H. M., very freq. in Thuringia); 10. Andrena 

 albicans Miill. (Kn.) ; 11. Halictus calceatus Scop. (Kn.) ; 12. H. nitidiusculus 

 K. 5 (Budd.); all po-cltg. (b) Vespidae: 13. Odynerus parielum L. 5 (Budd.). 



Loew observed the following in Steiermark (' Beitrage,' p. 46). — A. Diptera. 

 Syrphidae: I. Syrphus lunuiatus Mg., po-dvg. (?). B. Hymenoptera. Apidae: 



2. Halictus maiachurus K. 5, po-dvg. 



MacLeod observed in the Pyrenees one humble-bee, and 5 Diptera, as visitors 

 {' Pyreneenbl.,' p. 389). 



2. C. recta Z. (Herm. Muller, ' Fertilisation,' p. 69 ; Schulz, ' Beitrage,' I, p. i ; 

 Beyer, ' D. spont. Bewegungen. d. Staubgefasse u. Stempel ' ; Knuth, ' Bloemenbiol. 

 Bijdragen'; Kirchner, 'Flora von Stuttgart,' pp. 258-9.) 



While the last species generally exhibits slight protogyny, C. recta is feebly 

 protandrous. The white flowers are arranged in terminal paniculate cymes. When 

 they open, the stigmas are not yet fully mature, and are covered by the stamens 

 ^vhich closely invest them. The outermost of these at once bend outwards and their 



B 2 



