The following article is the beginning of a series of discussions on identifying features of various orchid species/genera.
A previous blog (see here) referred to the importance of the column in Thelymitra but did not give details of the parts of the column which is the subject of this blog.
The columns in a Thelymitra (Sun Orchid) may be one of the main identifying features of a sun orchid and so this article looks at those features that botanists will often refer to in their descriptions.
Though we cannot physically dissect an individual flower, we can make use of photographs to spot the various features.
The diagram below is that of T. ixioides (based on the taxonomy of 1984) column whilst the photographs are that of T. juncifolia column (as T. ixioides is now considered to be limited to the eastern states). The column of these two are similar. One photograph will not give all of the features hence in this article the three photographs show all of the features except the viscid disk where the pollinia is stored. The stigmatic plate is sticky and receives the pollen for fertilization.
Most of the variations between the Thelymitra columns occur within the upper portion of the column. The post anther lobe can be quite varied. For instance, with T. ixioides/T. juncifolia the post anther lobe is not hooded. Some with hoods may have deep splits, whilst others form a broad fringe. Yet again, others have variations within the column arms such as having no cilia. This will be dealt with in further articles.