86 INTRODUCTION. 
But in this position the pollinia would be useless, since they could never 
reach the stigma, as may easily be seen if the observer immediately 
attempts to re-introduce the pollinia on the pencil; but in from two to 
three seconds the caudicles or stalks of the pollen-masses become bent 
forward, through an arc of 90 degrees, into a line with the pencil, which, 
if then re-introduced, will carry the pollen-masses exactly on to the 
viscid stigma, and some of the grains of the former will adhere to it so 
as to fertilise it. This delay, before the caudicles bend forward, probably 
prevents the fertilisation of a flower by its own pollen, and, the insect 
then flying to another flower, affords the probability of cross-fertilisation, 
which Darwin has shown to be generally so advantageous to plants. 
In the case of Orchis mascula, the bending did not take place until after 
an interval averaging thirty seconds. Robert Brown had previously 
pointed out another arrangement, which is common amongst the tribe 
Ophrydex :—‘ The stigma is very viscid, but not so viscid as, when 
touched by a pollinium, to pull the whole off an insect’s head, or off a 
pencil, yet sufficiently viscid to break the elastic threads by which the 
packets of pollen-grains are tied together, and leave some of them on 
the stigma. Hence a pollinium attached to an insect or to a pencil 
can be applied to many stigmas, and will fertilise all.” (Darwin, ‘ On 
the various contrivances by which Orchids are fertilised by Insects,’ 
2nd ed., p. 18.) The process here described is, in its main features, 
that most common in all the Ophrydee. It may, however, be even 
more plainly seen in some of the larger Disas and Satyriums than in 
this species. 
Disperis Capensis.—In September, 1884, I examined 100 flowers of 
this species, and found that 13 had been visited by insects, of which 
only 7 had been fertilised. The details were as follows :— 
Both pollinia in situ ...... 88 stigma pollinated ......... 1 
One pollinium removed... 2 rs Pm doko er 2 
Both pollinia removed ... 10 Eh SO Me Eee 4 
The pollinia cannot be removed by the wind, or by a blow. The 
viscid dise of the pollinary glands appeared to be wanting in adhesive- 
ness. In this species and in several others which I examined, the 
caudicle, which may be said to extend the whole length of the 
pollinium, becomes strongly revolute in less than a second after 
withdrawal from the cell, in such manner that the granules (which 
are disposed in a secund order along each margin) stand out at a 
wide angle, and are then well adapted for striking the stigma when 
approaching it from very different directions. This is shown, as to 
another species, in Plate 19, fig. 6, though less forcibly, because the 
sranules and the curve are both smaller in that than in the present 
