48 THE ORCHID REVIEW. [FEBRUARY, 1923. 
arranged in whorls of three. ‘The three outer segments are called sepals, 
and in the adjoining illustrations of Dendrobium Farmeri and Cattleya 
Bowringiana, each one is marked with a letter S. In many of the popular 
genera, such as Odontoglossum, Lelia, 
Cattleya, and Dendrobium, the three 
sepals of any particular flower closely 
resemble one another in formation and 
colour. The odd segment at the top is 
known as the dorsal, or median, sepal, 
and the two lower ones as lateral sepals. 
In some flowers the sepals are developed 
to a comparatively excessive degree, so 
much so that they almost conceal the 
other segments. A noteworthy example 
occurs in Masdevallia amabilis,:in which 
the three sepals are united at their bases 
and form a tube-like structure. In Masde- 
vallias of the Chimera section the sepals 
are unusually well developed and form the 
chief attractive feature 
of these  curiously- 
formed flowers. The 
allied Cryptophoranthus 
atropurpureus (Masde- 
valia fenestrata) is a Petals, lip and column concealed within 
flower that greatly in- Bioko tenet 
terested Darwin, who remarked that it “is an extra- 
ordinary flower, for the three sepals always cohere together 
‘and never opén. Two minute lateral windows, seated 
high up in the flower and opposite each other, afford the 
only entrance into the flower; but the presence of these 
two minute windows shows how necessary it is that 
cRYPTOPHORANTHUS — Insects should have access in this case as with other 
ATROPURPUREUS, . 
ic Wek oe Orchids. At the bottom of the roomy and dark 
chamber formed by the closed sepals, the minute column 
is placed, in front of which the furrowed labellum stands, with a 
highly flexible hinge, and on each side the two upper petals, a little 
tube being thus formed. Hence, when a minute insect enters, or a larger 
insect inserts its proboscis through either window, it has by touch to find 
the inner tube in order to reach the curious nectary at its base” 
(Fertilisation of Orchids). 
In the genus Cypripedium it is the dorsal sepal that affords the chief 
MASDEVALLIA AMABILIS. 
