Within the Oncidiinae tribe of orchids are the two closely allied genera of Ada and Brassia. The genus Brassia
in particular includes a number of plants which produce spectacular 'spider' like flowers, and which are comparatively
easy to grow. Most species produce flowers which give off a pervading pleasant fragrance, especially during warm
daylight hours, which is an added attraction. For many years they have not been especially popular plants, but
are now being recognised for their true worth. Some hybridisation within the genus has taken place in comparatively
recent years, with also some intergeneric breeding completed, in some cases producing most interesting results.
As will be discussed later, the genus Brassia contains plants which fall into two main groupings, one of which
shows many characteristics which distinguish plants of the genus Ada; therefore this review from available literature
will cover both these genera.
The genus Brassia was founded by the English botanist Robert Brown in 1813. It was named in honour of William Brass,
a botanical artist and collector for Kew Gardens in the early decades of the nineteenth century. It is ironical
that as Brass collected mainly in South Africa, he was never in fact involved in the Central and South American
genus that bears his name. The first descriptions were on the basis of the species B. maculata, which had
been imported from Jamaica in the early part of the century (1806), and which was the first species to be cultivated
in Europe. Since the founding of the genus, some 74 species have at some stage been described as Brassias. The
majority of these have now, however, been reduced by synonyms in recent taxonomic studies, with only 2 to 3 dozen
valid species remaining.
In 1863 Reichenbach f. transferred all the Brassias then known into the genus Oncidium. Lindley in 1853, confirmed
that the distinction between the genera Brassia and Oncidium was slim. Brassias are distinguished by their very
short earless column, and a lip which is not lobed, bearing a callus of two parallel ridges, combined with elongated
lateral sepals. Because of their readily distinguished flowers, most botanists have continued to maintain the Brassias
as a separate genus, to save endless confusion with labels which would arise if amalgamation was confirmed, and
partly because there appears to be a distinction readily apparent to most growers.
Two major groupings of somewhat similar species of Brassias can be identified, and in 1853 Lindley sectioned the
genus into the Eubrassia ('true brassia'), similar to B. maculata, and the Glumacea, similar to the species
B. glumacea. The sections are distinct, the most obvious distinguishing characteristic being the large papery
floral bracts of the Glumacea, which sheath the pedicel completely as compared with the small basally clasping
bracts of the Eubrassia. The Eubrassia have prominent pseudo-
bulbs with 2 to 3 basal bracts, which never sheath the mature pseudobulbs. The Glumacea produce, on well grown
specimens, 2 to 3 inflorescences per growth; the Eubrassia only 1, or rarely 2.
The natural habitats also appear to confirm the establishment of the two subgenera. The Eubrassia extended at one
time from Florida throughout central America to northern America, principally in lowland fairly dry tropical areas,
although one species, B. verrucosa, is frequently encountered in high elevation cloud forests. The Glumacea
species are generally only localised in these higher elevation cloud forests.
In reviewing this genus, botanists found that the features which serve to distinguish Eubrassias from the Glumacea
are similar to the characteristics of the genus Ada. While this affinity is recognised, the genus Ada has not generally
been amalgamated with the Brassia glumacea species, although Williams, in 1972, did take this step.
The genus Ada was founded in 1854 for the single Andean species A. aurantica. There seems to be little affinity
between the Glumacea and Ada based on external flower form. However, on opening up Ada auranticia, a flower
is discovered con- forming in many ways to the Glumacea, except in its colour.