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Friday, 11 May 2012

Floating filamentous algae

One dish in two different roles, but
here comes a third way to use it:
In the last entry, I described a method for pressing specimens of land plants.

It is also possible to dry and preserve algae and seaweeds, though some of the thick plants like kelp can be a bit of a challenge. Some thick seaweeds can be pressed if they are soaked in hot water first, but you need to use hot sea water, because many of them just collapse in hot fresh water.

The one thing you must have is a shallow dish.  Mine is a bit of an antique: once it would have been used in the kitchen, but for me, it is everything from an algal culture receptacle to an ant lion home, and as I will explain, one of these days, even as a device for gauging rates of evaporation.

You can't just put the thin seaweeds in newspaper, because most of the algae will just bunch up into a dark clump. You need to 'float' them onto paper, so the parts spread out, and the second picture shows you how to do it.

Like the plant press in the last entry, it comes from my 1986 book, Exploring the Environment. I own the copyright and explicitly release this image into the public domain.

Get a fair sample of an alga into a shallow dish in water. Then slip a sheet of reasonably stiff card or heavy drawing paper underneath the plant. Once you have the alga positioned, slide the sheet out of the water, picking up the strands of the alga as you do, using a small artist's brush. Leave the sheet of paper to dry for a while on thick newspaper and then press it in the usual way.

You can improve on this method.  The one thing you can't leave out is the use of the brush to move the alga in the water. Using a backing board of some sort behind the paper may help. You may need to experiment with covering the more filamentous algae with plastic (on one side only!) when you put it into its first wrap of newspaper. With the back of the sheet uncovered, water will still escape.

The main thing is to know that seaweeds can be floated onto a flat surface.  After that, you are ready to go!

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