INTRODUCTION. 
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I.—GenrraL Remarks ON THE ORDER. 
Tue Order Orcume is one of the most natural and sharply- 
defined amongst flowering plants, containing about 5000 known species, 
the most numerous amongst Monocotyledons, and the third largest 
(after Composirrm and Lecumios#) of all Phanerogams. It is dis- 
tributed over almost the whole globe, most abundantly in the tropics, and 
is rare only on the highest mountains, in extreme Arctic and Antarctic 
regions, or in some of the nearly rainless desert tracts of the globe. 
It is most nearly allied to the Order Scrramive# (best known at the 
Cape by the beautiful Strelitziee of the southern coast districts); and 
has also affinities, though more remote, with the Order Inmrm. 
Orchids are distinguished from all other plants by four chief 
characters :—(1) By the consolidation of the stamens and pistil into a 
common mass, which is called the column; (2) by the suppression of 
all the anthers (normally six), except one, in the vast majority of the 
Order, or except two in Cypripediez ; (3) by the peculiar condition and 
arrangement of its pollen and the anther which contains it; (4) by the 
very general development of one of the petals (the lip, or labellum) in 
an excessive degree, or different or unusual form. To these may be 
added, ‘great variety of habit and diversity of station ; the immense 
variety of its peculiar and highly-specialized flowers; and the un- 
usually large number of seeds produced in one capsule.” * 
While it is often extremely difficult for the inexperienced botanist 
to understand the true nature of the peculiarities of the flowers of 
Orchids, yet their characters are so distinctly marked that a very short 
acquaintance enables the beginner to recognise an Orchid when he 
sees one. 
The extreme irregularity and variety in the structure and position 
of the floral organs of this Order led to a close investigation of their 
homologies by Robert Brown, Lindley, and Darwin. The following 
are the conclusions arrived at by the last-named, after a laborious 
* Herm. Miiller, ‘On the Fertilisation of Flowers.’ 
