Monocotyledons with Petaloid Flowers — Orchidacece. 
I 2 I 
Fruit a capsule, dehiscing usually by valves connected above and below. 
USES, &c.—Excepting for the purposes of ornamental cultivation, for which the singularity and beauty of the 
flowers of a large number of tropical Orchidaceae, eminently fit them, the Natural Order is of small direct import¬ 
ance to mankind. Vanilla, used to flavour chocolate and confections, is the dried capsules of Tropical American 
species of the climbing genus Vanilla. The tubers of a few terrestrial species of Orchis, abounding in gummy and 
farinaceous matter, are candied as a confection, and in the Isle of Bourbon the leaves of an epiphytal Orchid 
(. Angrcecum ) are dried for use as a stimulant tea. 
The Order is of peculiar physiological interest from the circumstance to which Mr. Darwin has recently called 
attention, in that, with very rare exceptions, self-fertilisation of the flower is mechanically impossible, the species 
being consequently dependent upon extraneous (insect) aid to secure the transfer of the pollen to the viscid stigma. 
The special adaptations of the structure of the flower, especially of the form and position of the lip, column, pollen 
and stigma, designed to secure insect aid and also to insure the transfer of the pollen from flower to flower, are 
exceedingly curious and well illustrated in common British species. 
Of ornamental species in common cultivation in our stoves and plant-houses we have, imported from Tropical 
America, numerous species of Epidendrum, Cattleya, Laelia, Brassia, Maxillaria, Oncidium, Odontoglossum, 
Catasetum, Trichopilia, and many others : from Tropical Asia and the Indian Islands, Dendrobium, Aerides, Sacco- 
labium, Eria, Phalaenopsis, Vanda and others. The Island of Madagascar affords us the magnificent Angrcecum 
sesquvpedale, the wax-like cream-coloured flowers of which measure 4-6 inches in diameter; the labellum bearing a 
spur of 16-15 inches in length. 
Natural Order 
IRIBACEHL Tab. 94. 
D 1 agnosis.— Herbs with radical leaves sheathing at the base. .Flowers 
perfect; perianth-tube adherent, limb 6-leaved. Stamens 3 with extrorse 
anthers. Ovary inferior, 3-celled. Seeds albuminous. 
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