Measuring spores and other microscopic details

[SheffieldLass]

Something I've been wondering about for a while, but not found anything written ...

Andreas recently confirmed that measuring the length of a spore is by a straight line, which makes sense, ignoring the curve on say a curved cylindrical spore. Well it is difficult to measure it any other way, but good to have that clarified ....

But how do you measure the width of a curved cylindrical spore? Across the widest point of the spore, or is it effectively the width of a rectangle that the spore would just fit in? There can be a considerable difference in the result.

I've just been measuring spores of a Daedaleopsis confragosa, which are curved cylinders, and it would appear that the rectangle method would be the correct one, at least fits the sizes given in the books, whereas the widest point on the spore comes in too small ... and that seems to be the case with other similar shaped spores I have measured.

Then of course there is the question of the apiculus whether that gets included in the width/length measurements .. I have assumed that it does ...

And of course trying to measure only the spores lying parallel to the plane of the slide, so that we are not measuring fore-shortened views. Anything else we should be aware of? Warty spores, measuring warts and all I presume ....

And then, how do you measure curved basidia ... I guess there you try to get a measurement close to the straightened out length. Also where is the width measured?

And what about cheilocystidia ... some seem to have 3 width dimensions (and one length). What is the convention there?

Melanie

[mollisia]

Hallo Melanie,

I'm not sure, whether to the points I answer now is a complety accordance between all mycologists, but I suppose it is.

Originally Posted by SheffieldLass

But how do you measure the width of a curved cylindrical spore? Across the widest point of the spore, or is it effectively the width of a rectangle that the spore would just fit in? There can be a considerable difference in the result.

I measure always the widest point. Most of the ascomycete spores are +/- elliptic and you always measure the widest point, I'm sure.

I've just been measuring spores of a Daedaleopsis confragosa, which are curved cylinders, and it would appear that the rectangle method would be the correct one, at least fits the sizes given in the books, whereas the widest point on the spore comes in too small ... and that seems to be the case with other similar shaped spores I have measured.

Hmm, I have never heared of this methode before and I'm sure that at least most of mycologists do not measure like this. I know Fred Kränzlin and also knew Sepp breitenbachh and I can assure you that in Fungi of Switzerland the spore width is given as the widest point.

There are some basidios which have threedimensional seen a width and a hight of the spores, e.g. in some Coprinus species. Those mitrashaped or rhomboid spores are measured in length, width and hight!

Then of course there is the question of the apiculus whether that gets included in the width/length measurements .. I have assumed that it does ...

Clear answer: No it is not included. Just measure the surrounding of the spore.

And of course trying to measure only the spores lying parallel to the plane of the slide, so that we are not measuring fore-shortened views.

Yes!!! Very important and very timeconsuming sometimes when you have a preparation with a few spores only. And then you can't measures them because they are not lying neatly on the side. Especially very very important when you want to identify Amanita subgenus Amanitopsis, because there it is very important whether the spores are perfectly round or whether they are subglobose. It is one of the first questions in the keys and leads to completely different groups. When you make an mistake already there, you come to completely different results ...

Anything else we should be aware of? Warty spores, measuring warts and all I presume ....

Again no, only the surrounding gets measured. An exception are spores with knots, like Entoloma or the Inocybes with the nodulouse spores. There also the nodules are measured, because they are not ornamentations, but outgrowth of the spore itself.

And then, how do you measure curved basidia ... I guess there you try to get a measurement close to the straightened out length. Also where is the width measured?

I wouldn't measure curved basidia. Except in species where they are always curved, like in some Heterobasidiomycetes. There I would try to measure the real length, means all the curve and not the direct way.
The width is measured at the widest point. May be there are cases where it is useful to give a width measurement from the base and a second one from the apex, but I don't remember an example.

And what about cheilocystidia ... some seem to have 3 width dimensions (and one length). What is the convention there?

Yes, that often happens and then you have to give three measurements. E.g. in Conocybe, where you have the length, the width of the lower part and the width of the head. Often also in Hebeloma, in Galerina and there are for sure many species where you have to describe the cystidia with more than two measurements.

An important point is also, in which medium you measure! Very very important in inoperculate ascomycetes, but also in other fungi. E.g. asco spores are often mounted in Cotton Blue for to see best the ornamentation. If you ever have done this, you will see, that the spores immediately get a kind of kidney-shaped. They implode! Of course if you would measure the spores in Cotoon blue, you get completely false results. All letal colorations cause an effect of shrinking to the cells, be it only small or be it very prominent as in the inoperculates (appr. 30% length and width lost there!). KOH in contrary has the effect to make elements bigger sometimes. That's why you use it to rehydrate Herbariummaterial.
So the best is, to mount all you want to measure in water only, at least when you have fresh material. But there are exceptions, e.g. in Russulales all people measure the spores in Melzers, and so one should do to be comparable. Cortinarius spores are always measured in KOH 3-5%, but there are no differences to water mounts according to my observations. And if you treat herbarium material, you usually have to work with KOH anyway.
The best is, you always make a note in which mount you measured, than it is always comparable.

best regards,
Andreas

[SheffieldLass]

Thanks Andreas for your very detailed reply.

It is so fundamental you'd think it would be described in the books! And I'm glad that the width of the spores is the measurement at the widest point. At least I don't have to go back and redo all my measurements ....

Regards

Melanie