Rhizodiscina lignyota

The Rhizodiscina fruit bodies were growing with a white, sheet-like fungus (probably a species of Hyphodontia) on the underside of a fallen, long-dead eucalypt branch in a suburban garden. The red scale bar in Photo 2 represents 1 millimetre. In Photo 3 you see several asci with mature spores (the latter generally about 12 x 4 microns). In Photo 4 you see a couple of immature asci and (in the inset) some of the dark brown to blackish, polygonal cells that make up the outer layers of tissue on the lower side of the fruit body. There's another sighting from the same area at: http://canberranaturemap.org/Community/Sightings/Details/3360812. Though both sightings are in the same suburban residential block, they represent two populations: one in the front yard, one in the back, some tens of metres apart, separated by a house and on two different substrates.

I have not yet come across a report of this species from Australia. There is one report of it from New Zealand and it is widespread in the Northern Hemisphere. There could be specimens of it in Australian herbaria (but not yet named) and there may of course be some published record that I have not yet found. It may be quite common, but the small fruit bodies would make this an easily overlooked species and I am curious as to how widespread it is in the local area. The focus of Canberra Nature Map is photographic records not specimens. Furthermore, in the ACT and NSW, permits are required for the collecting of fungi on various land types (e.g. nature reserves). If you hold such a permit or are able to collect from private land and come across tiny black disks (no more than a few millimetres in diameter) on wood, I would be happy to see them and have them lodged as herbarium material. If you do see such disks (and you may need a hand lens to make sure you have something disk-like since other small black things turn up on wood) all you need do is to cut of a small, thin piece of wood, large enough to hold a number of disks (the more the merrier). If the wood is quite dry then you need do nothing more. If the wood is damp then it will help to dry it (e.g. in front of a fan heater or on a sunny window ledge - and this will be easier and quicker if your piece of wood is thin). You can leave any specimens for me at the information desk at the botanic gardens. Please include your name (so you can be acknowledged as the collector on the herbarium label), location details and a brief note about the habitat and, if possible, the type of wood on which it was growing. Remember that my two sightings are from a suburban garden, so you might even find it, almost literally, on your doorstep! You can send me a message via Canberra Nature Map if I have left something vague or if you have any further questions.

Ostensibly, there is an early reference to this fungus in Australia (page 273, M.C. Cooke, Handbook of Australian Fungi, 1892) under the older name Karschia lignyota. Cooke's text reads: "Cups superficial, saucer-shaped, externally dark rufous, margin thin, soon flexuous (1. m.m.), disc rather concave, quite black; asci clavate, 40-55 x 12 mu, paraphyses copious, crowded together; sporidia oblong, constricted uniseptate, 10-16 x 3-4 mu, 2-4 guttulate, pale sooty brown. On rotten wood. Victoria. " and refers to Figure 171, which you can find here (http://www.cpbr.gov.au/fungi/cooke-plates/plate20.pdf), towards the lower right. One ascus is near the margin and to its left (connected by dotted lines) you see two loose spores and both face-on and side views of the saucer-like apothecia. Cooke uses the term 'sporidium' rather than 'spore' and paraphyses are the narrower, sterile filaments found between the asci and some appear in the photos. Cooke's fungus could well be Rhizodiscina lignyota but, ideally and to be sure, any specimens he saw should be re-examined to check for those features he doesn't mention.