THE ORCHID REVIEW. 
VoL. XIX.] OCTOBER, tIogIt. [No. 226. 
THE EVOLUTION OF THE ORCHIDACE. 
(Continued from page 69.) 
Tue subtribe Oncidiee is placed next to Maxillariee by Bentham, and now 
claims our attention. The group is entirely American, ranging from Mexico 
to Peru and Bolivia, and contains over forty genera and 750 known species. 
It is a very important horticultural group, and contains a large number of 
our popular garden Orchids, while representatives of most of the genera are 
occasionally met with in collections. The majority have a marked habit, 
by which they are easily recognised when not in flower. Oncidium and 
Odontoglossum may be regarded as typical of the group, but there are other 
genera which show a wide diversity in habit. The rhizome is usually short, 
but sometimes more or less elongated or creeping, and bearing short stems, 
generally terminating in a pseudobulb, crowned by one or two apical leaves, 
with a few distichous leaves or leaf-sheaths below the pseudobulbs. The 
latter are very various in shape, and sometimes they are almost sessile on 
the rhizome, and the scapes arise from the rhizome close to their base, 
while in a few genera the terminal pseudobulb is wanting, or only very 
tardily thickened out, and the leaves are either distichously imbricate on 
the short stem or form with the peduncles an apparently radical cluster. 
The leaves are coriaceous or fleshy, rarely membranous, and neither plicate 
nor prominently many-ribbed. The inflorescence is usually racemose or 
paniculate, and the flowers very various in structure, but the cclumn is not 
produced into a foot, so that there is no real mentum to the perianth, 
though in a few genera the lip or the lateral sepals, or both, are produced 
at their base into a short spur. The pollinarium is usually well 
developed, with a distinct stipes, while there is a great diversity in the 
shape and details of the perianth, and in the staminodial appendages which 
form the crests of the lip and the teeth and wings of the column. 
Bentham subdivided the Oncidiez into five subordinate groups, very 
unequal in size, but agreeing fairly well with the characters of the plants, 
and these we may now consider, arranging the genera, however, somewhat 
in the order of their progressive development. 
As constituting what may be termed Oncidiez proper, we find a group 
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