246 Oliver . — On the Sensitive Labellum 
experimental evidence which would confirm this view — how- 
ever, should it assist in this way, such a function is fortuitous 
and entirely secondary to that of limiting the angle covered 
in the movement. 
I do not find in other Masdevallias anything corresponding 
to this emergence. It has no doubt been developed in 
connection with the special mechanism of contraction, which 
exists in this member of the genus only, so far as is 
yet known. In Pierostylis — a genus of Orchids far removed 
from Masdevallia— a quite analogous arrangement is, how- 
ever. found. The labellum in this genus 1 is endowed with 
an irritability very much like that in Masdevallia muscosa. 
Figure 15 shows the relation to the column of the labellum 
both in the extended and in the contracted position (latter 
with dotted outline). In this connection I wish to call at- 
tention to the position of the emergence — e' and e" in the 
two positions respectively. There can I think be little doubt 
as to the emergence here preventing the labellum contracting 
beyond a certain limit ; further contraction will cease when 
the emergence strikes against the foot, ft. This figure gives 
us the case of P. Waolsii, Fitzgerald, but in the majority 
of other species the emergence does not project downwards 
in such a rigid manner, but is thin, flexible and very usually 
fimbriated at its edge. Thus Fig. 16 represents P. curia , 
R. Brown, and in this case it would offer no such efficient op- 
position to the continued contraction of the labellum : and 
from Fitzgerald's figures and an examination of dry material 
I am by no means sure that it would press against the foot 
even if the labellum very considerably overstepped its normal 
limit. The speculation may be hazarded that in this genus 
there was at first developed — in connection with the motility 
— an emergence which limited the range of the labellum. 
1 The facts relating to Pierostylis are drawn from R. D. Fitzgerald’s Australian 
Orchids, vol. i. Sydney, 1882. Mr. Fitzgerald gives a most interesting account of 
the part played in fertilization by the movement, and had been able to study the 
phenomena on the plants growing amid their natural surroundings. The two 
figures of Pierostylis (15 and 16) are schematised from his drawings. 
