Friday, September 23, 2011

Black Bootlace Orchid

Erythrorchis cassythoides (Galeola cassythoides)

It’s flowering time for this fascinating climbing orchid.

It’s a plant with no leaves at all, and is of the kind that is often called a “saprophyte”.

Most of the world’s plants need green stuff for survival. Chlorophyll is what makes leaves green. It’s a substance that is essential for photosynthesis, the process which is the plant equivalent of eating. Photosynthesis uses solar power to combine carbon (taken from carbon dioxide in the air) with hydrogen (from water, which is made of hydrogen and oxygen) to make carbohydrates.

Our bootlace orchid, however, has nothing green about it. Its rather evil-looking black bootlace stems come up from roots which are getting all the food the plant needs by being parasitic on certain soil fungi. The fungi, in turn, are growing on dead plant matter. The term “saprophyte” comes from sapro (decay) and phyte (plant). It means a plant that lives on decaying matter. Nowadays, however, the term is falling out of use, because it is now understood that the alleged saprophytes are really living on the soil fungi, which are themselves living on the decayed matter, Strictly speaking the plants are not saprophytes, but “myco-heterotrophs”!

Bootlace orchids climb up the trunks of their trees with these spongy, water-absorbing roots. For most of the year the plants are quite inconspicuous, but in spring they put out a great show of flowers.

They are closely related to a Mexican climbing orchid, Vanilla planifolia, the source of the vanilla we use for flavouring. You can see the bootlace orchid’s seed pod, which appears in February, does look rather like a vanilla pod.

Bootlace orchids are always found growing on eucalypts which are completely or partly dead - another good reason for not being too “tidy” about clearing away dead trees on our properties.

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