European Larch

Notes from a beginner
Pollen mounting for microscopy

by Keith Lester

I’ve been teaching myself to mount pollen samples for microscopy. It wasn’t a simple task, not knowing where to begin, but I’ve persevered, taken some amount of advice and finally have a method that works for me. If you’re interested to try it yourself, I can explain.
First, what do you need?

Pollen gel, I use Brunel’s version, but you could make your own. It’s a glycerine and gelatin mix with basic fuchsin red stain already added.

Alcohol, anhydrous if possible, ie 100%. I use isopropanol, aka rubbing alcohol, but you could use everclear, 100% ethanol.

A shallow dish, heatproof. I use a 50mm watch glass.

A source of heat. I used a spirit burner, but have just upgraded to a mug warming plate.

European Larch, 75-90 microns, x60 objective

Method:
Take a blossom, or a catkin, expose the pollen bearing organs. If it’s a flower you may have to remove a few petals. With catkins you can sometimes shake out the pollen. Shake, jog, or wash the pollen onto the watch glass by using a millilitre or so of alcohol. You can tell if you have any pollen by holding the glass over a strong light (the light source of your scope, perhaps). Any pollen grains will catch the light.

Swirl the alcohol gently in the watch glass to wash the oils from the surface of the pollen and the pollen grains should settle towards the lowest part of the glass. Allow the alcohol to evaporate until there’s almost none left. A mug warmer will speed up the process, using a flame is inadvisable as the alcohol may flare and burn.
Add a pea sized portion of pollen gel and put the glass to warm over your heat source. Once the gel has melted, mix it around to ensure it’s picked up plenty of pollen, draw some up into a micro-pipette and squeeze a small drop onto each of three or so slides.

Carefully put on a coverslip (I use round ones) and the gel should spread under the slip. If you’re a bit too slow, gently warm the slide from below and the gel will re-melt and spread. It takes a few tries to judge the correct amount of the pollen/gel to put on each slide. If you put too much, it bleeds out around the edges. Okay for a temporary slide but a nightmare to remove if you are going to ring the slide for a permanent reference. Nothing to it! 

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