Diderma?

[flaxton]

Can anyone give me even a family for this group growing on a birch leaf


Thanks
Mal

[stickman]

Hi Mal

I usually find these are either Diderma effusum or Didymium difforme, the latter being by far more common IMO.

The easiest way of seperating them is by spore size (they do have other seperating characters such as the nature of the peridium etc):

7-9 µm - Diderma effusum
11-14 µm - Didymium difforme

I'm not sure if they can be seperated reliably in the field - I have certainly not found any surefire method. It would be interesting to hear from others with experience of both species.

Cheers,
Nick

[flaxton]

Thanks Nick
Very mixed sized spores but plenty in the 12um region so rule out D effusum and to go with D difforme.

Mal

[Kevin Lawson]

Hello Mal,

I agree with Nick that this is Didymium difforme on the basis of your spore measurements.

With regard to seperating this from Diderma effusum in the field, I have found that Diderma effusum tends to form more extensive plasmodicarps (based on 4 finds of Didymium difforme and 19 of Diderma effusum). Though this is by no means foolproof and checking spore size is a reliable way of seperating the two.

I have found Diderma effusum to be more common than Didymium difforme.
This is probaly due to locality and habitat as all my studies are conducted in a single (though varied and extensive) wood on the outskirts of Swansea.

Regards,
Kevin