CHEESEMAN.—-On the Fertilization of the N.Z. Pterostylis. 355 
On several occasions I have artificially inclosed small insects in the flower. 
Most escaped by crawling up the column and passing between the appendages, 
and some, but not all, carried pollen-masses away with them. It can hardly 
be expected, however, that insects selected at random would remove the 
pollinia with the same ease and certainty as the species to whose requirements 
the flower has no doubt been profoundly modified by natural selection, acting 
during long periods of time. 
Although I have often watched the flowers I have never seen insects 
directly enter them. It occurred to me, however, that I should be more 
successful if I were to examine every plant noticed with the lip drawn back 
against the column. Acting on this idea I soon found three, each inclosing a 
small dipterous insect. Two of these had no traces of pollen on them, and 
the flowers were not fertilized. The third was dead, apparently not having 
been able to find the passage out of its prison. It had the remains of two 
pollinia attached to its back. The stigma of the flower was also plentifully 
covered with pollen, which had evidently been conveyed from another plant, 
for all four pollen-masses were intact and undisturbed in their cells, 
The fact of this insect being unable to effect its escape led me to examine 
a considerable number of flowers which had commenced to wither, and in 
which the sepals and petals had closed together, with the view of ascertaining 
if this circumstance was of frequent occurrence. The results were important. 
Out of 110 specimens examined seventeen contained dead insects, and nine of 
these insects bore traces of having had pollen attached to them. Some had 
followed the passage between the wings of the column until they had reached 
the anther, and then becoming glued to the pollen-masses had not been able to 
drag them out of their cells, thus perishing on the threshold of their prison. 
Many of the flowers which did not inclose insects exhibited signs, besides 
the removal of the pollinia, of having been visited by them, from the presence 
of hairs, etc., adhering to the stigma and rostellum ; and in one instance the 
antenna of some insect was found glued to the rostellum, proving that its 
owner had escaped by crawling through the passage in front of that organ. 
All the insects proved to be Diptera, and all are probably referable to one 
ies. I am not, however, entomologist enough to be able to indicate its 
name. What inducement there is to visit the plants I cannot conjecture, for 
even with the most careful examination I have not been able to detect the 
presence of any nectar, or nectar-secreting organs. 
The comparatively large number of insects retained in the flowers examined 
appears at first sight to show a serious imperfection in the contrivances for 
insuring fertilization, as it is evident that it is a loss to the plant when its 
visitor cannot escape and carry away the pollinia. On a closer examination, 
however, it probably only proves how carefully the passage for the exit of the 
