308 ANGIOSPERMAEDICOTYLEDONES 



During insect-visits the stigma first projects from the tip of the carina, and then 

 the pollen, both returning to the carina on removal of the pressure. 



Visitors. These are bees, of which I observed: i. Apis mellifica Z., skg. ; 

 2. Bombus agrorum F., do. 



718. R. viscosa Vent. ( = R. glutinosa Sims). (Knuth, ' Bloemenbiol. Bij- 

 dragen.') This is a North American species, not infrequently cultivated in Europe 

 as an ornamental tree. The flowers are of a bright flesh-colour, and arranged in 

 dense racemes. There is a bright yellow nectar-guide on the vexillum. The brush 

 on the style resembles that of R. Pseud-acacia. The upper free filament is fused 

 for about half its length with the staminal tube. 



Visitors. At Kiel and Rendsburg I observed two bees, freq. skg. (28. 6 to 

 1. 7. '96): 1. Apis mellifica Z. |jj; 2. Bombus lapidarius Z. jjj. 



217. Caragana Lam. 



719. C. arborescens Lam. (=Robinia Caragana Z.). 

 Visitors. Kirchner observed a humble-bee (Bombus lapidarius Z. ), skg. 



legitimately, in Wurtemberg (' Beitrage,' p. 43). 



218. Phaca L. 



Nectar-yielding bee flowers, usually yellowish or violet in colour; with simple 

 valvular arrangement 



720. P. alpina Jacq. (Herm. Miiller, ' Alpenblumen,' pp. 236-7.) In the 

 flowers of this species the nectar is concealed at a depth of 9-10 mm. The petals 

 are so close together that it is doubtful whether the numerous Lepidoptera that are 

 attracted by the marked conspicuousness of this plant succeed in reaching the nectar, 

 even when they have a proboscis of sufficient length. Probably only long-tongued 

 humble-bees are able to do this. It is doubtful whether self-pollination takes place. 



Visitors. Herm. Miiller observed 4 humble-bees and 9 Lepidoptera in 



the Alps. 



Loew noticed the following in the Berlin Botanic Garden. 



A. Diptera. Syrphidae: 1. Syritta pipiens Z., flying in numbers around the 



flowers and settling both on the alae and the carina, po-dvg. (?). B. Lepidoptera. 



Rhopalocera : 2. Pieris napi Z., skg. 



721. P. frigida L. (Herm. Miiller, 'Alpenblumen,' pp. 237-8.) In this 

 species self-pollination is possible in the Alps in individual cases. According to 

 Axell ('Om Anord. for Fanerog. Vaxt. Befrukt.,' p. 17), the flowers are homogamous 

 in the Scandinavian highlands; but Lindman says that the anthers ripen in the 

 bud, before the stigma becomes receptive. In this region automatic self-pollination 

 takes place in fully matured flowers when the weather is favourable, but when it 

 is fine crossing is effected by the agency of humble-bees. Hermann Miiller observed 

 that, from the first, the stigma usually projects a little beyond the stamens; and 

 it is only in individual flowers that the pollen surrounds the stigma so that automatic 

 self-pollination takes place. 



Visitors. These are undoubtedly humble-bees, but the species which actually 

 effect cross-pollination have not, so far, been determined. 



