Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Saturday, September 25, 2010

"rufa Greenhoods" - another "first" for me

Today I went to Yalwal, south-west from Nowra, to a place where Alan Stephenson had showed me last autumn. The reason? To see the Oligochaetochilus rufus (otherwise known as Pterostylis rufa) which are to be found in this spot.

This is the first time I have seen this species, in flower.

When I first "got into" Orchids I became fascinated by the many shapes of Greenhoods, and then I discovered that some "greenhoods" were red. That's when I first realised the mystery of Greenhoods - which lay in front of me.

Regular readers will recall that I published a post about the "Gibbosa Greenhoods" several weeks ago. And then the related "bicolor Greenhood" the next day. Both those plants are related to this plant, which is the "nominate species" for what is known in Orchid circles as the "rufa group" of Greenhoods. Yet the similarities are not in colour (for both those two plants are green). No, the primary similarities lie in the shapes of their "labellums" and their dome-shaped "hood" (galea) and the wide flange under the galea which is nearly closed off. There are other factors, such as the leaf rosettes and the sheathing stem leaves. Anyway, that's all getting a bit technical - sorry.

To me, this is a very exciting "first" for me, because these plants are quite iconic for me, for the reasons given above. So lets look at the plants themselves.
Oligochaetochilus rufus - a profile view.
Note the deflexed lateral sepals underneath the hood.Here is a lovely plant with three flowers and several buds yet to open.
It is relatively tall for this species,
but it is still only about 6 inches high (12 cm approx).
Here is a lovely pair of plants growing in close proximity.
These were barely 4 inches high.
The open flowers were even lower than that (buds above yet to open).
Here is the most distinctive feature of this plant
- the labellum with stiff hairs.
These hairs are long, all around the sides and the lower edge.
There is a band of short stiff hairs across the upper edge of the labellum.
Here is the botanical illustration for this species from PlantNET.
Here is my best cropped image of the "labellum".
You can see how well drawn is the image above.
Here is another plant with the labellum having been triggered (closed).
You can see the yellow "hinge" of the labellum,
which is now closed right up inside the galea.
With the stiff hairs all around the labellum,
any insect which might have triggered the movement sensitive hairs
would be "imprisoned" inside the galea,
being unable to squeeze out past these stiff hairs.
The labellum relaxes and opens after some time, freeing any insect
which might have been trapped inside.
That is a technique designed to help the plant achieve pollination.

The "gibbosa" had a quite different shaped labellum.
It had only two of these long, stiff hairs.


Dr Dave said...

I miss all the ground orchids that would pop up around Canberra and the coast each spring after good winter rains. Sure we have orchids in Kuranda but you need a ladder to see them in the tree tops!

Enjoy the ground orchids before the "fire season" arrives. They ahve started to burn up here already!


Denis Wilson said...

Hi Dr Dave,
It always seems a strange coincidence to me that CSIRO and the ANBG (Botanic Gardens) ended up being located on Black Mountain in Canberra which is reputed to have more Orchids on it than the entire island known as England.
I don't know if you knew David Jones, formerly of the National Herbarium, but all he had to do was walk 300 metres and he would be in a rich "Orchid habitat".
Even the moths, and doubtless the beetles, of Black Mountain were excessively studied.
It seems ironic, to me, that for a dry mountain, on infertile soil, it turns out to be such a great habitat.
Re your comment on Epiphytic Orchids vs Ground Orchids, I drove down Barrengarry Mtn yesterday (near Kangaroo Valley) and saw a lovely large spray if Orchid flowers 30 metres up a huge tree.
Even a "long lens" was no good for that.
Cheers to you, Dave.
(For general readers, Dr Dave is a retired entomologist, formerly of CSIRO in Canberra, now luxuriating in insect heaven at Kuranda, far north Queensland.)

Red Nomad OZ said...

Looks like it's a pretty good year for orchids - here in SA the spider and donkey orchids are amazing! Alas, I don't know the botanical names, but enjoy them nonetheless!

Happy travels!!

Denis Wilson said...

Hi Red Nomad OZ.
Enjoy your Orchids in SA.
You can learn more about them, once you learn to love them.
That's the most important bit - loving them.
I miss Spider Orchids - they don't like the soil around where I am.
But we do have lots of other lovelies, plus the bizarre tiny things.
Thanks for commenting.