z^o ANGIOSPERMAE—DICOTYLEDONES 



Visitors. — Hermann Miiller saw po-cltg. bees, most of which also bored for 

 nectar (Bombus lapidarius L. 5 and 5, skg. and po-cltg. ; B. terrester L. $, skg. ; 

 Andrena albicans Mull, j, po-cltg. ; A. tibialis K. ; A. xanthura K. 5, po-cltg. ; Apis 

 mellifica L. 5, freq., po-cltg.), also moths (Plusia), skg.; and Meligethes, creeping 

 about the flowers. He noticed both bees and butterflies that, not merely in one 

 flower but in several successively, inserted their proboscis under the vexillum, and 

 remained in this attitude for some time. Under such circumstances the collecting 

 apparatus of the bees remained quite empty after repeated visits. From this it 

 may be concluded that bees and butterflies actually perforate and suck the 

 nectariferous swelling. 



In Kiel Botanic Garden, I saw (May 21, 1896) the just-opened flowers of 

 laburnum visited by our three commonest humble-bees, po-cltg. (Bombus hortorum 

 L. 5, B. terrester L. 5, B. lapidarius Z. 5). 



Alfken observed the following bees at Bremen, all skg. — 



I. Bombus agrorum Z'. 5; 2. B. hortorum Z. 5; 3. B. ruderatus Z'. 5 ; 4. 

 Psithyrus vestalis Fourcr. 



648. C. decumbens Spach. — According to Briquet ('£tudes de bid. flor. 

 dans les Alpes Occident.'), the flowers of this species are nectarless, and possess 

 an explosive mechanism which acts but once. It is set free by humble-bees, and 

 cross-pollination often results. Automatic self-pollination takes place in wet weather 

 (Kirchner). 



649. C. hirsutus L. — 



Visitors. — Schletterer records the bees Podalirius acervorum Z., and P. larsatus 

 Spill., for the Tyrol. 



650. C. nigricans L. — Hermann Miiller describes (' Weit. Beob.,' II, pp. 254-6) 

 the flower mechanism of the golden yellow flowers of this species as being an 

 intermediate stage between the pumping arrangement of Lotus (vide supra), and 

 the simple valvular arrangement of C. Laburnum. The alae enclose the uppermost 

 part of the carina, which narrows into a sharp edge, and are slightly convex 

 externally. Their lower margins rest on the expanded sides of the carina. In 

 the young bud the five very large outer stamens (i. e. those alternating with the 

 petals) project completely beyond the five very small inner stamens (superposed 

 upon the petals). The anthers of the large stamens dehisce before anthesis, and 

 quickly shrivel, so that their pollen lies loosely between them, surrounded only 

 by the carina. The tips of the filaments of the small stamens have so far been 

 bent inwards, but they now straighten themselves, forcing their anthers between 

 those which have already dehisced, and pushing the pollen shed by these into the 

 empty upwardly-bent tip of the carina. The thickened outer filaments are stiff', 

 and when the carina is depressed push out the pollen through the opening at its 

 apex. These filaments therefore act as piston-rods, while the small anthers, filling 

 as they do the lower part of the pollen receptacle, serve as pistons. In a young 

 flower, depression of the carina — the upper edges of which are closely apposed — 

 causes some pollen to be squeezed out of its apex, so that it will adhere to the 

 under-side of an insect visitor. But, in older flowers, the upper carinal edges are 

 so loosely in contact that when the carina is depressed it opens widely, allowing 



