243 
of Masdevallia muscosa , Rchb . f. 
crest. Within a second of stimulating the crest the blade is 
moved upwards through an angle of some io°, then for a brief 
space, which is only just appreciable and amounts to a small 
fraction of a second, a slight hesitation or slowing, as it were, 
is noticeable, and finally the upward movement is continued 
through a further angle of 70° or 8o° with great rapidity. 
The whole process barely occupies two seconds 1 . In Fig. 4 
the position of contraction is shown. By this act an almost 
entirely closed space is temporarily formed. The space is 
bounded posteriorly by the column, and anteriorly by the up- 
folded blade. The foot forms the floor, and three-fourths of the 
side parts are closed by the lateral sepals. The two lateral 
petals complete above the blocking of the sides (the position 
of one is represented in Fig. 4 by the dotted outline Ip.) and 
form a partial roof. Fig. jo represents a flower looked down 
upon from above, the blade, bl., being in the elevated position. 
The anther, a, is borne on the summit of the column of which 
the dorsal ribbed surface, c, is visible. The two pollen-masses 
project from the anther along the top of the rostellum (cf. 
Figs. 8, 9, and 10). The rostellum, r., projects slightly into 
the space (e, Fig. 10) left between the two lateral petals, 
l.p., which, considerably over-stepping the column, meet one 
another anteriorly. The distal surface of the blade, bl., is 
seen drawn up and preventing any outlet between it and the 
two lateral petals. 
A glance at Figs. 4 and 10 shows that the anther is not 
included in the closed space. From this it may be inferred 
that, should we have here a device for promoting cross-fertili- 
zation by insect-agency, it is no part of the plan that the 
insect captured should be confined within the flower till the 
labellum moves down again. Rather, on the other hand, is it 
essential that it should make its escape through the aperture 
described (e, Fig. 10), for this is the only means by which the 
pollinia can be removed. To this point I shall return. 
1 This account applies to flowers only for the first four or five days after opening. 
Subsequently, as they begin to pass off, the movement is more sluggish. Flowers 
will often last for fourteen days before withering. 
