G. M. Tuomsox.—On the Fertilization of some New Zealand Orchids. 491 
margin is the rostellum. This is formed of large cells, covered with a very 
delicate membrane. If this be touched with a bristle, it is almost instantly 
ruptured, and a small, very viscid drop of matter exudes, In withdrawing 
the bristle the pollinia are brought away with it. The anther is terminal 
(posterior), and has broad lateral projections. The pollinia are four in 
number, in two pairs, and in the form of plates. The flowers do not appear 
to secrete any nectar, but when the surface of the labellum is slightly 
punctured, a considerable amount of sweetish purple juice exudes, which is 
probably grateful to insects. From the shape of the flowers, it is necessary 
to cut them longitudinally to see the parts. Looking at the position of the 
anther and stigma, it appears to me almost impossible that self-fertilization 
can take place; at the same time it is somewhat difficult to suggest any 
satisfactory way in which an insect could accomplish either this or cross- 
fertilization. I presume that any insect entering the flower would have to 
back out again by the same way as it entered, and in doing so it would 
come in contact with the rostellum, and would remove the pollinia on its 
head. It is also probable that, in endeavouring to obtain from a second 
flower any of the sweet juices from the tissue at the base of the labellum, it 
would slightly advance its head, so as to bring the pollinia attached to it on 
to the stigma. Again, it is possible that self-fertilization might be secured 
by an insect thus getting the pollinia on its head, and then endeavouring to 
push its way down through the small lateral apertures. In doing so, it 
would almost certainly smear the stigma with pollen from the same flower, 
and I have sometimes been inclined to think that such did take place. At 
the same time, this would seem like putting an unnecessary difficulty in the 
way of what is usually a very simple process, and therefore no great value 
is to be attached to this idea. 
For a time I could not understand why spiders frequented these flowers 
so much, but I soon found a sufficient cause. The only insects capable of 
removing pollen which were found about the flowers were small Diptera— 
probably a species of Culex. In several cases these small flies had penetrated 
into the tube of the flower, and, in their eagerness after the sweet juices 
found there, brought their heads in contact with both rostellum and stigma, 
and partly owing to the viscidity of these parts, and partly to the narrowness 
and bending of the tube, were unable to withdraw backwards. In some 
flowers insects were thus found still alive, in others they were dead, while 
in many others only portions of them, such as legs, wings, etc., were left, 
the spiders having devoured the rest. In every case in which a captured 
insect was withdrawn from its trap, the pollinia were removed also, securely 
attached to the front of the head. ; 
I closely examined 143 flowers, and found that in 47 the pollinia were 
