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30-11-2025 12:53

Edvin Johannesen Edvin Johannesen

White short-stipitate apothecia found on thin twig

30-11-2025 10:47

William Slosse William Slosse

I recently found a collection of small Peziza sp.

27-11-2025 12:01

Thomas Læssøe

https://svampe.databasen.org/observations/10496727

27-11-2025 11:46

Thomas Læssøe

https://svampe.databasen.org/observations/10493918

17-09-2025 10:50

Heather Merrylees

Hi there!I am hoping for any advice on the identif

29-11-2025 08:40

Andreas Millinger Andreas Millinger

Hello,on a splintered part of a branch on the grou

28-11-2025 16:45

Nogueira Héctor

November 23, 2025 Requejo de Sanabria (León) SPAI

25-11-2025 14:24

Thomas Læssøe

https://svampe.databasen.org/observations/10490522

27-11-2025 15:41

Thomas Læssøe

Spores brownish, typically 4-celled; 26.8 x 2.4;

27-11-2025 11:31

Thomas Læssøe

Collectors notes: Immersed ascomata, erumpent thro

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Black dots on maple leaf
Alan Rockefeller, 31-12-2013 11:00
Alan RockefellerGrowing on Acer macrophyllum (bigleaf maple).  Seen at the Yuba Watershed Fungus Fair.

No asci observed. Many parathyses with tiny oil drops were seen, they measured 30 – 45 × 2 – 3 micrometers. Many clavate basidia-like things seen, however they never had sterigmata or spores inside. Those measured (28) 36 – 47 x (5) 7 – 8 micrometers.

  • message #26494
Jacky Launoy, 31-12-2013 12:58
Re : Black dots on maple leaf
Rhytisma acerinum (Pers.:Fr.) Fr.
David Malloch, 31-12-2013 15:34
David Malloch
Re : Black dots on maple leaf
Hi Alan..
That is probably Rhytisma punctatum.  The US host-index lists it on Acer macrophyllum in California, Oregon and Washington.  The "clavate, basidia-like things" are probably immature asci.  These would be mature in the spring at about the time the new leaves are emerging on the tree.

Dave
Byrain, 31-12-2013 16:47
Re : Black dots on maple leaf
Alan, I found that leaf and posted it on MO as Rhytisma punctatum.  I have the other two leaves from that collection also.  I scoped them too and also saw no mature asci.

Here are some more macro images... http://mushroomobserver.org/156379?q=1higi?

Edit:  I understand that punctuate dots like this on Acer macrophyllum = R. punctatum, but there is another species with a somewhat similar appearence on other maples.
http://www.glfc.forestry.ca/VLF/ForumPresentations/hsiangtarspot_08e.pdf