268 Sargent. — ■ Notes on the Life-History of Pterostylis. 
of communication between the chambers is the narrow passage or tunnel 
between the column-wings. An inwardly directed wrinkle on each side of 
the galea, extending some distance upwards from the base, considerably 
narrows the entrance to the lower chamber. The labellum fits this doorway 
pretty closely (Fig. i). 
When the flower is open and ready to receive visitors, the labellum leans 
forward against the visor. In this position its tip protrudes a little from the 
flower and forms a convenient platform for insects to alight upon. The 
remainder of the lamina forms a sloping pathway down into the lower 
chamber of the galea. On the insect’s arrival at the base of the lamina, the 
labellum suddenly springs back, hurling the insect against the stigmas. The 
lamina now leans against the column-wings (Fig. i), thus closing the lower 
chamber’s doorway, and making the insect a prisoner. The insect may 
remain a prisoner till the automatic door falls open, which it will do in about 
half an hour ; or it may at once escape by means of the tunnel between the 
column-wings. This course is most favourable to the flower. The tunnel 
narrows considerably towards the top, and once an insect arrives at this 
narrow part retreat is almost impossible. 
The escaping prisoner makes his way through the tunnel with his back 
towards the column ; and, when passing through the narrow part, its back 
cannot fail to come in contact with the sticky face of the rostellum, which is 
situate at the top of the column in front (Fig. 5). The anther, which is 
hinged to the top of the column behind the rostellum by a very short band 
of connective, partly obstructs the exit from the tunnel, so that the insect in 
emerging must lift it slightly. Each cell of the anther contains two bacilli- 
form pollinia lying quite loose in the cell, one above the other. When an 
insect lifts the anther, the part of its back rendered sticky by contact with 
the rostellum comes against one or two of the rods of pollen, and these, 
adhering, are carried away from the flower. When free from the tunnel 
nothing remains to hinder the insect’s departure. The flowers of P . con- 
stricta , nana, pyramidalis , and recurva, differ so little from that of P. 
reflexa , that I need not describe them ; but it will be well to point out the 
conspicuous differences found in the flowers of the other Westralian species. 
In these the visor is sharply reflexed at its base, and hangs down in front of 
the ovary, and the labellum hangs down in front of the visor. In P. vittata 
the lamina is a small oval fleshy plate, and its appendage a mound of tissue, 
surmounted by a slightly hairy spike. In P. rtifa the lamina is a fleshy rod 
without any specially differentiated appendage. In P. Sargenti the structure 
of the lamina is particularly remarkable. It mayibe described as consisting 
of three lanceolate segments conjoined at the base, but free above for fully 
half their length. Each outer segment bears at its base a large flattened 
clavate appendage, which leans inwards, so that the apices of the two con- 
nive. Immediately behind these appendages there is a ridge of tissue, which 
