parr.) | THE MECHANISMS OF FLOWERS. 229 
inner stamens even for some time after the outer anthers have 
dehisced, and such flowers therefore are essentially proterandrous 
_ (609). 
136. GEUM RIVALE, L.—The honey exudes in numerous minute 
drops from the base of the receptacular tube, and is diligently 
sought by humble-bees while most of the flowers are still in the 
bud. Bombus terrestris, L. 9, which steals honey from many 
‘different flowers, sucks honey in Gewm rivale also from the -outside 
‘in yet unopened flowers, thrusting in its proboscis between the 
‘sepals and petals. Even after the flower is expanded, B. terrestris 
often, and other species of Bombus occasionally, obtain the honey 
in this way; but for the most part humble-bees hang suspended 
to the flower, which they grasp with their mid and _ hindlegs, 
putting their forelegs and head inside the flower. The outer 
_ portion of the honey they seem to reach more easily from the 
outside. This liability of the honey to be reached from the out- | 
side is a serious imperfection in the flower, which thus gets deprived | 
_ of its honey without receiving cross-fertilisation in return. 
The flowers are proterogynous, and in young flowers the ripe 
stigmas project far beyond the still closed anthers. Cross- 
fertilisation is thus insured if at this time a bee inserts its head 
in the legitimate manner. Later, the stamens elongate till their — 
anthers stand on a level with the outermost stigmas ; in dehiscence, — 
the anthers cover themselves all round with pollen. When the 
flower closes, the anthers are brought in contact with the outer- 
most stigmas, and self-fertilisation results, unless the pollen has 
been removed by bees. Since the plant grows sheltered in woods, | 
_ it is visited by numerous bees even in unfavourable weather. 
According to Mr. T. Whitelegge, @. rivale is occasionally andro- | 
-moncecious (774). 
_ Visitors: A. Hymenoptera—Apide: (1) Bombus terrestris, L. 9 ; (2) B. 
| lapidarius, L. 2; (3) B. confusus, Schenck, ? ; (4) B. hypnorum, L. ? ; (5) 
| 8B. pratorum, L. 9 §; (6) B. Scrimshiranus, L. 2 $; (7) B. hortorum, L. 
2%, very ab. ; (8) B. agrorum, F. 9; (9) B. fragrans, K. 9, very scarce ; 
| (10) B. senilis, Smith, 9; (11) B. silvarum, L. 9, ab., all sucking (B. sil- 
_ yvarum, 2, and B. pratorum, §, also collected pollen, hanging back downwards 
_ to the flower) ; (12) Apis mellifica, L. $, sucking the flowers from outside, 
_ab.; (13) Andrena helvola, L. 9, seeking vainly for honey. B. Diptera— 
_ Syrphide (14) Rhingia rostrata, L., very ab.,s. and fp. C. Coleoptera— 
Nitidulide : (15) Meligethes, ab. 
» Geum reptans, L., and G. montanum, L., are proterogynous and 
__androdicecious; that is to say, besides the ordinary individuals 
