Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Monday, February 04, 2008

Chiloglottis Orchids are out in force, now.

This is very satisfying to report. Three different species of Chiloglottis Orchids in a single day's outing. I went out with Chris, a fellow member of the Illawarra branch of the Australasian Native Orchid Society. Chris is an expert photographer, and he has an excellent website, which you may visit here. I have also linked to Chris's Orchid gallery, via my Aussie Orchid sites links on the right.

These little Orchids are known in general terms as "Wasp Orchids" (a reference to their main pollinating insects). Previously they were known as "Ant Orchids", or even "Bird Orchids" as the first species described held their flower open to the sky, and supposedly resembled the mouth of a young bird, begging for food. Under new taxonomic revisions, both those names are now reserved for separate groups of related plants.
This first species is new for me. Chiloglottis sylvestris. I first found these plants this time last year, just after the last flower had been pollinated. However, I could not conclusively identify it then. These flowers close over, once they have been successfully pollinated, making photography of the distinguishing features impossible. The labellum (the lip, with the insect-shaped gland on it) rises up to close over the "column", protecting it from further disturbance or interference from insects.

In case you are wondering: "How does the plant know it has been pollinated?" The answer is that hormonal signals are sent from the ovary of the plant, causing the plant to enter a different stage of its development. That fact is a timely reminder that plants are indeed sentient organisms. That simple sentence would have been regarded as heretical in earlier centuries - and might have had me burnt at the stake. But I stand by that statement.

Incidentally, that argument is further supported by the amazingly complex relationship between these plants and male insects (mostly wasps) which pollinate them by pseudo-copulation. That topic has been discussed before, here, and back in 2005, here.

This flower has been photographed from over the top of the flower, to show the positioning of the "clubs" (the lateral sepals). Also, it shows the main gland as not being divided, (as a distinguishing characteristic from the other two species discussed below). The slight "V" shape of the labellum is an optical illusion, because of the angle of this photo. The upper photograph shows the true shape of the labellum.Anyway, last year I worked out what this plant might be, but I could not be sure, at the time - for the reasons stated. The first distinguishing feature is the habitat where these plants are growing. It is entirely different from the habitats where I have seen related species growing. I have been able to confirm the identity from the reddish colour of the flowers, the shape of the "pseudo-insect" (with an undivided "head"), and also the lack of reflexing of the "clubs". The short height of the stems (little more than two inches (50mm) and small size of the flowers is also a "fit" for this species. These are really tiny "Wasp Orchids" (and the other ones are not large).

These plants are growing in heavy shade, under dense cover of Tea Trees and Melaleuca scrub, in a muddy creek bed. The area is wet most of the year, and especially at flowering season (now - when it is raining constantly outside, as I write this post). These plants may well be under-water today. These plants are in the general Belmore Falls area, about 5Km south of Robertson. This plant is known to be at its southern limit of its distribution at Robertson.

The next species is a plant which I identified last year - the appallingly named "Turtle Orchid" (because an early botanist thought that the tiny "glands" on the labellum looked vaguely like a turtle, with its long neck protruding). The name Chiloglottis seminuda, is a reference to the labellum having a bare area at the lower end. (Other species share that feature, but it was named to distinguish it from others which have a larger area of the labellum covered with glands). This second species was growing in heavy black soil, derived from Wianamatta shale, over a sandstone rock base. The forest cover is tall Eucalypt forest, with mixed Proteaceous shrubbery - Waratah country.

Here are new photographs of Chiloglottis reflexa, which I reported on two weeks ago - it was a new species (for me) at the time. These specimens are probably more diagnostic. Here you can see the divided "head" of the pseudo-insect (gland). It looks almost heart shaped. The lateral sepals, (the "clubs") spread widely, and then curve right down and under the flower and almost curl back up again. In profile, you can see how "reflexed" those clubs really are - almost touching back up to the top. That feature is how this species earns its name. The fairly large bare area of the labellum of this particular plant is not typical. Others in the same cluster of plants had much larger areas of cover of glands over the labellum. But the reflexed "clubs" are diagnostic. These just happened to be the clearest photographs I was able to get yesterday. The first flower in the previous posting (click here) has better gland development. It is the same species, growing in the same colony of plants as these plants shown today. This third species was growing in sandier soil than the second one, and less than one kilometre away from the location of the second species. While the forest cover in both places is similar, it is slightly more open, and the soil is definitely drier and sandier, as the ground is raised, being over a small sandstone outcrop. Species two and three are growing in East Kangaloon, about 5 Km north of Robertson.

Here are three images together in an attempt to give you the comparative features of the structures of the glands of these 3 species. The identification of these species does not hinge solely on the gland structures, but it is a good place to start. Unfortunately, at this level of cropping there is a great distortion of detail introduced into the image. But it is worth doing, for educational purposes, if somewhat disappointing, artistically. Click on this triple image to blow it up to a larger size, to allow a better look at the structures of these glands.

No comments: