Bulbophyllum macranthum , and allied Orchids . 333 
give so detailed a description of its fertilization as I could of 
the preceding species. It appears, however, that a minute fly 
enters the flower between the sepals, presumably in search 
of nectar, and climbs upon the nicely balanced lip, with 
its head towards the base of the lip. Its weight overbalances 
the lip, and it is thrown headfirst into the arms of the column 
(Figs. 7 , 8 ). The stiff erect petals play the part assigned 
to the stelidia, preventing the insect’s escaping on either side, 
and the pollinia are planted between its eyes (Fig. 9). In 
this plant the insect cannot use its wings on account of the 
sepals being too close together, so that when once it gets 
on the lip it must go headfirst into the column. In these 
small-flowered species it is absolutely essential that the lip 
should be very delicately balanced, on account of the very 
light weight of the small fertilizer, and this I believe is the 
reason of the extreme mobility of the lip. I do not think 
it plays any part in attracting insects, although it is true 
that the lip quivers more in the species with open flowers 
than in those with closed or partially closed ones. But in 
the latter case the insect cannot use its wings, so that, even if 
the motion of the lip is slow, it is quite sure, and the fly 
cannot avoid falling with its head on the column. On the 
other hand, in open-flowered plants like Cirrhopetalum the 
fertilizer must be taken by surprise, and be suddenly pitched 
off, or it would escape ; and for this it is essential that the 
lip should be exquisitely balanced. 
In the typical Cirr hope tala, e.g. C. Cumingii , the lateral sepals 
are connate for most of their length, and the lip hangs in the 
space between their bases. The sepals are the most conspicuous 
portion of the flower, and it is probable that they form the 
alighting place of the fertilizer. The lip is separated from 
the margin of the sepals in front by a considerable space, so 
that a small insect wishing to get at the nectar at the base 
of the lip cannot do so without getting upon it. There is a 
small-flowered species of Cirrhopetalum here which is of very 
remarkable structure, and is apparently undescribed, in which 
I have seen the fertilizer at work. This species has the 
