Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Wednesday, July 04, 2012

Orchids found amongst the Leeches

These Tall Greenhoods (Bunochilus longifolius) were the reason I got my "cut-throat Leech" I wrote about yesterday (an answer to Kirsten's question on Facebook).

Portrait of Bunochilus longifolius
Note how the Labellum is "set". 
It is highly sensitive and snaps upward, when triggered by an insect (also by casual movement of the flower - such as being bumped by the photographer).

The purpose of the sensitive labellum is to trap insects temporarily, inside the hood, to help initiate pollination. The insect gets trapped inside the hood, and the pollinia are sticky and if the insect touches them they attach to it. You can see where the "pollinia" are located within the "Galea" (hood). After the labellum snaps closed, it stays closed for approximately 30 minutes. Then the labellum relaxes, and opens naturally, allowing the insect to escape, hopefully with the sticky pollen grains attached, to wing its way to another flower.

It sounds a hit or miss system of pollination, but it has been working for Orchids for some 15 million years, according to evidence found recently in  fossilized plant resin (amber) which shows evidence of ancient insects carrying equally ancient pollen grains.

Leaves of non-flowering plant
of Bunochilus longifolius
Leaves of Bunochilus longifolius
this plant is developing an upright stem and the
long, pointed leaves, from which it earns its name.
Flowering stem of Bunochilus longifolius

This flower of Bunochilus longifolius
is fresh and the lateral sepals
(which sit below the labellum)
have not yet separated
They normally split up the middle.
You can see what I mean in
the bottom of the image immediately above.

These plants flower in a Melaleuca squarrosa thicket, which is found in a small stream-bed, along the Belmore Falls Road, several kilometres from Robertson. The Melaleucas grow very densely, creating dense shade. Apart from some ferns, very little grows as ground-cover in the middle of the thicket. There is very dense fern growth and dangerous Sword Grass clumps just outside the thicket, but once you get in the centre, there is very little other plant growth, apart from the closely set stems of the Melaleuca trees.

This season has been much wetter than previous years, and so the lower end of this thicket is now permanently wet (with between 3 and 6 inches) of permanent water, flowing slowly through the thicket. The "soil" here is actually deep leaf litter consisting of peaty material formed by the tiny leaves of the Melaleuca trees above.


catmint said...

the way the orchid traps insects is like a carnivorous plant except it doesn't digest the insects but releases them after a while. Everywhere weather seems to be changing ...

Denis Wilson said...

Thanks Catmint
I had never drawn the parallel between Carnivorous plants and Orchids before.