Classification of Orchid Genera 4

This is part four of a compilation of five instalments that first appeared in the Nambour Orchid Society newsletter between June and October 2021.

In the tribe Epidendreae, there are two very large subtribes, Laeliinae with 38 genera and 2580 species, and Pleurothallidinae with 35 genera and 4471 species, and four smaller subtribes. Plants in this tribe are sympodial, having pseudobulbs or reed stems and the inflorescences usually emerge from the top of pseudobulbs or reed stems. There were some significant changes to this tribe between the publication of Vol 4 of Genera Orchidacearum in 2006 and the Chase et al classification in 2015. I am following the latter document.

Dealing with the smaller subtribes first, Subtribe Bletiinae has four genera, two of which are of horticultural interest, Bletia (49 sp.) and Chysis (33 sp.). Bletias are distributed across Neotropical America. They are more terrestrial than epiphytic, even though they are in Tribe Epidendreae, growing in soils that are acidic and humus-rich. Bletia purpurea, left, is an example.

The Genus Chysis, native to Central and northern parts of South America, is gaining in popularity, particularly amongst species growers. Chysis liminghii, below right, is one of the more striking species.

The Subtribe Ponerinae with 4 genera and a total of only 23 species is if little horticultural interest.

The Subtribe Capypsoinae with 13 genera and 78 species includes the Genus Coelia which has 5 species, some of which are seen at shows. Coelia bella, left, is one of the more commonly exhibited.

The subtribe Agrostophyllinae contains only 2 genera, Agrostophyllum with 100 species and Earina with 7. Agrostophyllum occur from the Seychelles through tropical Asia and Malesia with the centre of diversity in New Guinea where 75 species occur. Groups of flowers typically emerge from grass-like stems. Agrostophyllum brachiatum, below right, occurs in the highlands of New Guinea.

The subtribe Laeliinae, often referred to as the Cattleya Alliance containing many species and around 46,000 registered hybrids is very popular with hobby growers. The facility to cross breed across the 38 genera has led to many intergeneric hybrids. The reclassification in GO Vol 4 caused major disruption as species were transferred between genera based on molecular studies of DNA. The more significant changes were:-

Agrostophyllum brachiatum
(photo by J. Cara)

The cluster type Cattleyas, bowringiana, skinneri, aurantica and hennisiana (syn. patinii) were transferred to a new genus, Guarianthe,
Brassavolas digbyana and glauca were transferred to Rhyncholaelia,
The Brazilian Laelias (sub-genus Hadrolaelia) were moved initially to Sophronitis and then all Sophronitis were transferred to Cattleya,
Some Schomburgkia were transferred to Laelia, the balance to Myrmecophila.

I expect that most readers will be familiar with the more common genera in Laeliinae but few would appreciate that the genus Epidendrum is the most numerous with 1413 species. Some species have reed stems but others such as Epidendrum stamfordianum, right (W. Harris photo), have pseudobulbs.

Encyclia, native to Central and South America, comes next with 165 species. Noted for open but often showy flowers, Encyclia cordigera, right, is a striking example.

Encyclia cordigera
(photo by C. McMonagle)

Prosthecea, distributed across Neotropical America, with 114 species is next. Some species are highly scented, Prosthecea fragrans being an example. Prosthecea prismatocarpa, below left, illustrates one of the attractive colour combinations in this genus.

There are 113 species and around 18,000 registered hybrids in the genus Cattleya. This is not counting a similar number of intergeneric hybrids in which Cattleya is part of the parentage. The genus is divided into 4 groups, each ranked as sub-genera. The Labiate group covers the exhibition type flowers generally with large showy labellums. The Bifoliate group is distinguished by plants having slender pseudobulbs and two leaves per bulb. Flowers of this group are brightly coloured, often with spots. C. schilleriana, below, is an example. The third group contains plants previously described as Brazilian Laelias. The fourth group contains plants previously known as Sopronitis. These are typically small, brightly coloured and well shaped.

There are only two species in the genus Rhyncholaelia, digbyana and glauca, both native to Mexico and Nicaragua and featuring in the parentage of over 19,000 progeny. The genus was separated from Brassavola by Rudolf Schlechter in 1918 but the re-classification was largely ignored, including by the RHS Register, until confirmed on GO Vol 4 in 2006. The photo below of Rhyncholaelia digbyana illustrates the large fimbriated labellum so valued by hybridisers over the past 130 years.

The genus Guarianthe was also separated from Cattleya in GO Vol 4. There are only 4 species in the genus, listed on the previous page, all characterised by clusters of strongly coloured flowers.

Prosthecea prismatocarpa Rhyncholaelia digbyana C. schilleriana Broughtonia sanguinea
(photo by W. Harris) (photo by C. McMonagle) (photo by C. McMonagle) (photo by C. McMonagle)

The genus Laelia was reduced by the transfer of the Hadrolaelia group of Brazilian Laelias to Cattleya. Offsetting this, some Schomburgkias were transferred into Laelia. Some Laelias have very long inflorescences. Laelia superbiens, pictured below right, is an example.

Laelia superbiens
(photo by C. McMonagle)

The genus Brassavola contains 22 species, widespread across Central and South America, the most common being Brassavola nodosa, noted for its large and spotted labellum.

Broughtonia, found only on islands in the Caribbean, is a small genus (6 species) noted for clusters of flowers having small flat labellums. Broughtonia sanguinea, above right, is the most widely known, featuring in over 1000 hybrids.

Caulathron (4 species) and Isabelia (3 species) are occasionally seen in collections.

Myrmecophelia is a small genus, originally proposed by Rolfe in 1917 to describe a group of species having hollow bulbs inhabited by ants (Myrmecophia means ant-loving) but they were left in Schomburgkia until transferred in GO Vol 4. The most popular species in cultivation is Myrmecophila tibicinis, left.

There are several other genera in Laeliinae but I conclude this subtribe with mention of Arpophyllum (3 species) and Barkeria (17 species). Arpophyllum are different from most other Laeliinae in that they many flowers arranged around an upright inflorescence up to 40cm long.

Literature cited

Chase M. W., Cameron K. M., Freudenstein J. V., Pridgeon A. M., Salazar G., Van Den Berg C. and Schuiteman A., An updated classification of Orchidaceae, Botanical Journal of the Linnean Society, 177, 2015 151-174.

Pridgeon A. M., Cribb P. J., Chase M. W. and Rasmussen, F. N., Genera Orchidacearum, Vol 1 1999, Vol 2 2001, Vol 3 2003, Vol 4 2006, Vol 5 2010, Vol 6 2014, Oxford University Press.

Author: Charlie

Classification of Orchid Genera 3

Classification of Orchid Genera 5