PART III. } THE MECHANISMS OF FLOWERS. 401 
Vincetomrcum officinale, L., is fertilised by the proboscides of small 
flies, Stapelia hirsuta, L., and S. grandiflora, Mass., by Musca 
6 vtoria and Sarcophaga carnaria, which are attracted by the 
‘putrid odour of the flowers. As a rule, in those Asclepiadez in 
which fertilisation is effected by an insect’s proboscis (Araujia, 
Cynanchum, Vincetoxicum, Stapelia, Boucerosia), the five nectaries 
alternate with the stamens; in those in which fertilisation is 
: effected by the legs of insects (Asclepias, Gomphocarpus, Centro- 
_stemma, Hoya), the: reverse holds ; in Stephanotis, which is fertilised 
y the proboscides of nocturnal Liidoptera, the base of the tube 
of the corolla forms a large honey-receptacle (172, 352). 
: In Ceropejia elegans, Wall., the flower forms a temporary prison 
f for its visitors, very much like that of Aristolochia COlematitis, L. 
Small flies (Gymnopa opaca) creep through the tube of the flower, 
which is at first erect, into the expanded portion which surrounds 
the reproductive organs; in this expanded portion, or cage, whose 
entrance is surrounded by stiff hairs pointing inwards, they are 
imprisoned for a whole day. On the second day these hairs wither, 
the flower bends over, the flies creep out with the pollinia attached 
to their proboscides, and seek new flowers, in whose cages they 
introduce the pollinia into the slits leading to the stigma, and get 
~ new pollinia attached to their proboscides (178, 360). 
— Cynanchum Vincetoxicum, R. Br.—The flower agrees in most 
points with that of Asclepias Cornutt. 
_ The dirty-white flowers of Cynanchum, devoid of the pleasant 
_ perfume of Asclepias, are adapted for fertilisation by carrion-loving 
_ flies, which convey the exceedingly minute pollinia, not with their 
_ claws, but with the bristles on their proboscides. Further, while 
- in Asclepias Cornuti the foliar appendages of the anthers form five 
fleshy cups filled with honey alternating with the corpuscula, here 
_ the same appendages of the anthers form high vaulted fieshy bodies 
coherent into a ring; and alternating with them are five deep 
BP ctariferous pits immediately below the five corpuscula. Into 
these pits, insects thrust their proboscides, to suck the nectar. 
When Muscide (in which the proboscis is set with erect bristles) 
“do this, it is almost inevitable that when the proboscis is being 
drawn back, one or other of its bristles gets caught in the slit, 
“which i is placed over the nectary and is Rider below than above ; 
after entering the slit, it glides upwards between the lateral anthers 
"wings of the two neighbouring anthers, straight into the inferior 
wedge-shaped notch of the corpusculum, and is there held fast. 
When the fly now gives a slight pull backwards in order to free 
DD 
4 
f 
‘ 
¥ 
We 
