PART III. | THE MECHANISMS OF FLOWERS. 517 
Darwin supposes that the flowers of Brugmansia are visited 
legitimately by long-billed humming-birds, but that short-billed 
humming-birds bore through the corolla and steal the honey (164). 
Rafflesia Arnoldi, R. Br., Horsfieldi, R. Br., and Patma, Bl., are 
probably fertilised by carrion-flies (178). 
Orv. ARISTOLOCHIAC EL. 
Asarum europeum, L., and A. canadense, L., are proterogynous 
with short-lived stigmas. In the first stage the stigma is mature, 
and the twelve anthers are still at the base of the flower. In the 
second stage the stamens grow up, arch over the stigma, and 
dehisce outwards. The fertilisers, in Delpino’s opinion, are small 
flies (177). 
Asarum may be looked upon as an incomplete stage in the 
development of the prison of Aristolochia (589). 
Heterotropa asaroides, Mor. and Dene.—The flowers are interme- 
diate in structure and in the mechanism of pollination between 
Asarum and Aristolochia. According to Delpino, the involute 
edge of the ventricose corolla forms a temporary prison for the 
insect-visitors, which are probably flies (178, 360). 
375. ARISTOLOCHIA CLEMATITIS, L.—The remarkable structure 
of this flower, which was long the only example known of a tem- 
porary prison for insects, was so far unravelled by Sprengel’s acute 
and patient observations, that Hildebrand’s investigations have 
brought nothing new to light, except the fact of proterogyny and 
consequent cross-fertilisation (349). 
The erect tube of the corolla is in the first stage lined with 
reflexed hairs, which permit small midges to creep down into the 
~ lower wider part which affords them shelter, but prevents them from 
creeping up again. In this cage the insect-visitors find the stig- 
mas mature, and fertilise them with pollen brought from flowers 
visited before, the anthers meanwhile remaining closed. On the 
withering of the stigmas, the anthers open; the tube of the flower 
bends downwards; the hairs wither and release the prisoners, 
laden with pollen, to fertilise other flowers which are still in their 
first (female) stage. 
Among numerous small species of gnats which I took in 
hundreds from the flowers of Aristolochia Clematitis, Herr Win- 
nertz identified the following : 
(a) Chironomide : (1) Ceratopogon sp. ; (2) Chironomus sp. ; (0) Bibionide : 
3) Scatopse soluta, Loew. 
