2 39 
of Mctsdevallia muse os a, Re Jib. f. 
shorter emergences, is at right angles to the scape. The 
sepals are triangular, and produced into long tails (see Figs, i 
and 2), yellow, with reddish nerves. The labellum — seen in 
the contracted position in Fig. 1, and in the expanded in 
Fig. 2 — is roughly triangular and articulated by a delicate 
hinge to the foot. It possesses a median crest on its upper 
surface, on stimulating which the labellum is immediately 
drawn up into the flower. The two lateral petals, right and 
left of the column, are quite narrow, and their distal ends (Ip) 
are seen projecting over the labellum in Fig. 1. The further 
details of the essential parts of the mechanism are given in full 
below. Reichenbach places the species in a group with Mas - 
devallia Echidna , M. Xipheres , and M. erinacea. 
Special Account of Labellum. 
The labellum naturally falls into two segments. These are 
(1) a narrowed proximal flexible region, which I shall always 
refer to as the neck (h in Figs. 3, 4, 7, &c.), which is articulated 
to the foot, ft ., — a downward prolongation of the column ; (2) 
a distal end-segment, triangular in form, the blade (bl. in Figs. 
3, 4, &c.). The neck then is the region intermediate between 
the foot (from the insertion of the emergence e) and the 
blade. 
The triangular blade has a slightly convex under-surface, 
marked by three low ridges (Fig. 5), which run mesially and 
right and left of the median plane respectively. Each ridge 
corresponds to a vascular bundle which runs in the subjacent 
tissue. These three bundles run continuously throughout the 
labellum, and are for the most part parallel, but towards the 
distal edge of the expanded blade they diverge considerably. 
On the upper surface of the blade is a most conspicuous 
median crest, commencing about 1 mm. from the distal end, 
and, after attaining a height of 1 mm., dying out in the region 
where the attenuated proximal comer of the blade passes into 
the neck. It is coloured a deeper yellow than the rest of the 
blade, due to the presence in its epidermis of very numerous 
yellow chromoplasts. Its broad distal part is coloured a deep 
