Once you have collected a fertile frond and it has released its spores, we hope the following will help you master the technique for separating the spores from the inevitable chaff which will have been shed as well.
First, an example where the collection time was pretty perfect and we have collected mostly spores.
Two days after collection, the frond has shed and the outline of its structure can be seen in the pattern on the paper. Although in this instance most of what you can see is actually spores, there is also some paler chaff.
This chaff is less sticky and more mobile on paper than the spores are, so tilting the paper at about 30 degrees to the horizontal and tapping gently underneath will generally move the chaff down the slope away from the spores. Doing this over another sheet of paper means the chaff will slowly collect on this and hence be discarded, as shown in the following picture.
As the spores also move down the slope, eventually you need to gather them together again to see how much contamination there is left. Folding the paper in half with the spores inside and flicking lightly with your first finger will generally bring all the spores down into the fold. Doing the same thing again at right angles to the first fold brings them to a single pile, as shown below.
You can see that, although there are a lot of spores, there is also a dusting of paler chaff which is especially visible around the edges. This can be separated from the spores by tilting and tapping as before, ending with fully clean spores. You may need to carry out the re-gathering and tapping process more than once if there is a large amount of chaff.
This picture shows the completed cleaning process. You can see the contrast between the fine dark spores and the much coarser pale chaff.
There are some species which produce pale spores. The process is similar for these, but in this case the chaff is darker coloured.
If the timing of collection is less optimum and there is a lot of chaff, spotting and cleaning the spores can be a little more difficult.
In this example, although it looks superficially similar, a lot of what you can see on the paper is chaff.
The process to follow is identical – tilting and tapping – and once again the more mobile chaff is moved away to reveal the darker spores underneath.