190 MR. Т. Н. CORRY ON ASCLEPIAS CORNUTI. 
of the same flower from which the pollinia have just been extracted, or from those of a 
neighbouring one. In doing so it repeats the same actions which it exhibited in its pre- 
vious search ; for, scrambling onwards and creeping with its feet on the smooth surface, it 
progresses manifestly with difficulty and in a very unsteady manner, since it is continually 
slipping. It is thus in its efforts naturally enabled to get one of its feet caught in the 
notch-like expansion of one of the alar fissures. If the foot so caught happens to have 
one or more pollinia attached to it, these are quite easily inserted into the alar chamber 
through the expanded notch when the insect, endeavouring to free itself, raises the leg to 
which they are appended upwards in the channel of the chamber. Owing tothe peculiar 
movement of the pollinia, described above, the more strongly convex border of each of 
them is turned away from the observer and towards the alar fissure, and is in front when 
the pollinia are inserted into the alar chamber through the notch. From this edge alone, 
as will be seen more fully hereafter, the pollen-tubes are emitted. If the movement did 
not occur on the part of the pollinia their broad surfaces would lie at right angles to the 
alar fissure, and their insertion into it in this position through the notch would in conse- 
quence be rendered a much more difficult, if not an altogether impossible operation; or 
else the pollinia in being slipped in would become folded in the opposite direction, and 
the less curved border, which emits no pollen-tubes, would be first inserted into the 
fissure. By raising its foot still further the pollinia, after being introduced into the alar 
chamber, are drawn upwards, one slightly in front of the other, the breadth of the 
innermost part of the alar chamber not being sufficient to allow them to go abreast. They 
proceed upwards until the most convex point of the more curved edge of one of them is 
opposite to, and in contact with, the point where the outer sloping portion of the base of 
the style-table abuts against the apex of Ше staminal column, $. e. with the true 
stigma. This portion of the alar chamber has been modified into that form which is 
precisely the best to receive the pollinia and to maintain them firmly in a position where 
they can effectually insert their pollen-tubes into the stigmatic tissue, and is, in short, 
so adapted to the form of a pollinium that it is no exaggeration to say that it appears 
almost as if it were the mould in which the pollinium had been cast. Above the point 
now occupied by the widest portion of the pollinium the alar chamber, whose dimen- 
sions gradually decrease upwards, becomes of such a limited area that it is unable to 
admit of the further passage upward of two bodies of such large size as the pollinia 
are. As the insect, therefore, by a powerful pull, overcomes the slight resistance which 
it experiences*, and extricates its foot, it tears across the “appendages,” which con- 
nected one or both of the pollinia to the corpusculum and are never very strong, 
leaving the pollinium hanging, firmly caught in the alar chamber opposite, and close 
to the true stigma. Тһе pollinium so abandoned is no longer visible from the exterior, 
but is completely hidden, and can only be seen on removing the anther-alae by sec- 
tion. Thus the pollination of the flower is accomplished, identically the same mechanism 
so ingeniously serving both for extraction of the pollinia and for their subsequent 
insertion. The corpusculum, along with its two broken appendages, is carried off by 
* This resistance is easily felt in artificial pollination. 
