Today I found a small colony of Chiloglottis growing in a damp area under a Melaleuca squarrosa thicket in a creek-bed. The area is on a sandstone plateau, and surrounding the creekbed thicket is dense Eucalypt forest and Proteaceous shrubbery. Outside of the thicket is a dense surrounding growth of coral fern. Parts of the thicket are permanently wet (creekbed) with Sphagnum Moss beds. Other areas are simply thick beds of leaf mulch from the Melaleuca trees above. So, what we have is a dense, dark and wet creekbed. At ground level, the shade is probably rated at about 70% shade cover.
In an area about 200 metres from this site,(across the road, in the same creek) is a similar thicket, where there is less leaf mulch, and the creek has a fine mud base. Over there Chiloglottis sylvestris grows. But having just inspected those plants, immediately before finding these plants I could immediately see these were different. The standard C. sylvestris plants have all now closed their flowers, following pollination. These plants appear to be a little larger than the regular C. sylvestris plants, but they are totally green, whereas the regular plants have stems and flowers which are reddish-purple, with black and purplish-red "glands". These plants are all green. Even their glands are green, but in different shades of green.
I have only photographed a single flower, but there is a second flowering plant, which is just opening. It is also going to be fully green.
Examining the shape of the glands in close detail it is apparent that these have the same shape and "distribution" on the labellum as C. sylvestris, but they are lacking the dark pigment. Also, in this flower, there are no dark spots on the base of the column (the tall part of the flower holding the pollinia). This may be contrasted with the lower photo of C. sylvestris (below).
Here is a similar angled view of the labellum and glands of one of the regular C. sylvestris plants from across the road, 200 metres further down the same creek.
This next view shows the regular C. sylvestris in profile, with the glands highlighted, appearing almost transparent. The shape of the main callus (gland) is not divided in the "head", unlike C. reflexa and C. seminuda, both of which occur in the Robertson region, but which prefer drier habitats in Eucalypt forest over sandstone soils.So, on the basis of the shape and distribution of the glands on the labellum of today's plant I conclude that these plants are a green variant of Chiloglottis sylvestris. But it is noteworthy that, although separated by only 200 metres from the other plants, and in a slightly different habitat (moss and leaf mould, instead of a muddy creekbed) these plants are flowering a full month later than their neighbours.
This morning I received the following note from Alan Stephenson, of the Illawarra Branch of the Australasian Native Orchid Society:
- Congratulations you have found an alba form of C. sylvestris. "Alba" normally means white but the same genes which produce white flowers also produce green flowers and they are considered the same. Last year I found an alba form of Nemacianthus caudatus and I have also found an alba form of Eriochilus cucullatus. Most species can produce an alba form but these are not common, although I have seen quite a few alba flowers of Glossodia major and Glossodia minor but never a Chiloglottis. The more you look the greater variety of flower types you will find.