This article is a completion of the Thelymitra Column article which appeared in the NOSSA Journal, Volume 42 No 8 September 2018. Click here for Part One.
The first part looked at the features and terms used by botanists to describe various parts of the column, a major identification feature of the sun orchids.
And as previously stated we cannot physically dissect an individual flower, but we can make use of photographs to spot the various features.
The diagram below is that of T. nuda (based on the taxonomy of 1984) column whilst the photographs are that of T. glaucophylla column (as T. glaucophylla is one of the T. nuda complex). The column of these two are similar.
The number of photographs may have been few but the quality was present. The clear winner was Claire Chesson’s Thelymitra glaucophylla (Glaucous Leaf Sun Orchid). Flowering from October to December, this endemic grassy woodland species of the ranges was only published in 2013 by Jeff Jeanes in the Mulleria 31:3 – 30 (2013) but it had been recognized much earlier by Bob Bates and has appeared with this name in his electronic Orchids of South Australia since 2005. It belongs to the T. nuda complex, of which there are 15 species, six of them having only been published in 2013. This complex is characterised by having large scented blue multiple flowers that open freely.
Not seen in this picture is the leaf and though the leaf is highly variable – 10-50cm long, 8-20mm wide, erect and short, long and flaccid, Jeanes mentions that T. glaucophylla “can be identified with a high degree of confidence from the mature leaves alone” (Page 4 Vol 31, 2013 Mulleria). The main features of the leaf are grey-green glaucous ie white bloom and is often senescent (withered) at anthesis (full flowered). Of the T. nuda complex, T. megcalyptra is the most similar but its leaf is never glaucous and has a red base, as well as an earlier flowering time and habitat of plains and rock outcrops.
For more details on the other orchids in the T. nuda group see the post titled Those Blue Orchids Again …posted 30th January 2015 with the link to Jeanes article in the Muelleria
By way of introduction, Muelleria is the Royal Botanic Gardens of Melbourne official research journal and has been published since 1955.
Though a technical article there is much to be gleaned for the ordinary reader, for instance the article contains a good description of the commonly used terms for describing the column for example stigma, trichomes, anther, post anther lobe, etc. This is helpful to know as the column structure is often the main feature of the plant used to identify the individual species. Naturally the key features of the T. nuda complex are covered comprehensively, as well as a brief discussion of the taxonomic history.
Another helpful section is the dichotomous key for all fifteen species described in the article. Of the fifteen species four are found in South Australia and are pictured below. But to discover more read the article ……