Journal Number 93
November 2005


HISTORICAL REPRINT

Lessons on Corybas taxonomy
From the introduction to John Dransfield, J. B. Comber and G. Smith.
A synopsis of Corybas (Orchidaceae) in West Malesia and Asia. Kew Bulletin 1986; 41 (3): 575-613.


Corybas is a remarkable genus of largely terrestrial orchids comprising about 100 species found from South China and India to New Zealand and the Subantarctic and Western Pacific Islands.

All species are small and inconspicuous from a distance; plants consist of a single underground tuber and a single leaf subtending a single flower. Although inconspicuous from afar, plants are often extraordinarily beautiful when examined closely and have a special jewel-like quality.

Structurally the flower is remarkable for the elaboration of the dorsal sepal and lip which together form a tube with an expanded mouth; the lateral sepals and petals vary between long tentacle-like structures and almost invisible threads; the lip usually bears two spurs. Everyone who has written about Corybas has waxed poetic over the charm of these "botanical jewels".

Unfortunately differences between taxa of Corybas which are strongly manifest in the field, tend to disappear in spirit material and dried pressed specimens are very difficult to interpret. Add to this the facts that some taxa are very widespread (e.g. C. carinatus) whereas others are known from one collection only (e.g. C. vinosus) and that two or three taxa may be found growing together, and there arises a great potential for confusion.

This paper arises from the frustration experienced in trying to identify species of Corybas from Peninsular Malaya, followed by the realisation that names used in Malaya were applied to taxa quite different from the taxa in the type country. Further, during the last ten years we have been able to accumulate a series of colour transparencies which, more successfully than any other method, have recorded the habit and colours of the flowers and shown distinctions, where none were originally thought to exist. Finally during fieldwork in West Malesia in 1977 during our spare time, we found an extraordinary abundance of Corybas and so it was possible to study variation between populations.

Originally it was our intention to prepare a paper giving field notes and illustrations of the species of Corybas known to us in the Malay Peninsula and Java, and to describe the species thought by us to be new. However, as might be expected, it has not been possible to prepare such an account in isolation - we have thus considered all species in the West Malesian and Asian region as well as those we know in the field in Sumatra, Java, Borneo and Malaya.

Obviously no satisfactory account of the genus can be prepared without monographic treatment;
a monograph of the species east of Wallace's Line has recently been undertaken by Dr P. van Royen and we hope that our work will complement his. We believe that field experience is essential in interpreting species in this genus. If in monographic work some of our new species prove to he synonymous with previously published taxa, we hope at least that our descriptions, spirit material, colour photographs and line drawings will be sufficiently clear and unambiguous to allow synonymy to be established easily. Confusion will still occur in the genus until the early, often inadequately, described and illustrated species have been refound.

Some of our conclusions are of a preliminary nature; we are conscious of erring on the side of over description, especially in the complex of C. pictus, but we feel it important to record the variation and disjunctions we have observed in the field. Unfortunately we have not been able to locate types of all species, but in our account we have indicated all instances where uncertainties of identity remain; when species have previously been well-described and illustrated, we have not duplicated the description, confining ourselves to new or poorer described or confusing taxa.

Hunting for Corybas is an exciting pastime. After some experience it is possible to predict where the orchids occur, and we have had the satisfaction of finding new taxa in otherwise well botanized localities. Often two neighbouring mountain peaks will carry completely different species of Corybas; sitting exhausted on the summit of a peak in Borneo or Sumatra and looking at high ridges and peaks leading off in all directions, we have often imagined the wealth of new records and taxa that must be waiting to he discovered. Furthermore no Corybas spp. have been recorded for Thailand, Vietnam, Laos or Cambodia, yet there must surely be species there. So we expect that as mountains are explored, new records and new taxa will be discovered and, we hope, greater appreciation of variation will be built up.


Diagnostic Characters

During our investigations of Corybas we have found certain characters to have been particularly useful in separating taxa and so it seems important that these should he discussed in some detail.

Leaf.  Although there is great variation in leaf size and even in shape within populations, some leaf characters are of diagnostic importance. The coloration of the venation is usually consistent, and presence or absence of crystal bundles, visible as white dots, seems to be consistent and useful. Undulation of the leaf margin is variable but its absence is usually diagnostic.

Lateral sepals and petals.  Relative size, orientation and presence or absence of connation are of great value.

Dorsal sepal.  Shape. coloration, and presence or absence of keels are of importance; however, in some species even within populations, the overall shape may be variable.

Lip.  Coloration and papillosity are useful features. One character to which we have given great emphasis is the shape of the throat and the related presence or absence of swellings at the mouth of the throat. We have found few useful characters apart from coloration in the spurs. Characters of the lip margin which have proved to be useful are the orientation and the nature of the denticulation.

Flower posture.  In a few species the flower seems more or less consistently to be reflexed.

Fruit.  Fruit is too rarely correlatable with flowers, but even when it can be correlated, we have found no features of diagnostic value.

 

 

 

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