Exidia nucleata

Description

Exidia nucleate is a translucent-white jelly fungus whose principal field mark is the presence of whitish nodules in the context. It can occur in extensive patches, becoming convoluted and brain-like in shape.

It is a common, wood-rotting species in Europe and North America, typically growing on dead attached or fallen branches of broadleaf trees.

Common names: Crystal Brain Fungus, Granular Jelly Roll.

Mushroom Identification

1. Sporocarps

   Fruiting body sessile, at first subglobose, becoming convoluted to cerebriform, often fusing into sheet-like masses up to 20 cm long, 5 cm wide, and 0.8 cm tall; surface glabrous, translucent-white, aging pinkish-tan to vinaceous-brown, occasionally olive-brown; context gelatinous, colored like the cap, tending to liquify in old specimens, with one or more embedded, but not anchored, cream-colored nodules; odor not distinctive; taste mildly fungal.

2. Spores

   Spores 9.0-12.0 x 4.0-5.5 µm, sausage-shaped, smooth, thin-walled, contents granular; basidia cruciate-type producing four epibasidia; spores white in deposit.

3. Habitat

   Scattered to fused into large groupings, e.g. broad rows or sheets, found usually on shaded, lower surfaces of decaying hardwood logs; fruiting throughout the winter months after rainy periods; occasional.

Look-Alikes

1. Tremella encephala

   Whitish when young, but the latter is pale yellowish-tan, not vinaceous-brown in age. More significantly, while Tremella encephala have a whitish core that mimics the nodules of Exidia nucleata, it is anchored at the base, not free within the gelatinous context. Other differences include a conifer habit and spores that are ovate, not sausage-shaped.

2. Exidia thuretiana

   Another hardwood inhabiting white jelly fungus. It can be distinguished by the lack of nodular inclusions and significantly larger spores.

3. Tremella mesenterica

   Usually yellow and has a brain-like structure, but it does also have a (rare) white form.

History

The basionym of this species was established in 1822 by American mycologist Lewis David von Schweinitz (1780 - 1834), who named it Tremella nucleata. Its widely accepted scientific name Exidia nucleata dates from a 1921 publication by another American, Edward Angus Burt (1859 - 1939).

Some authorities, particularly those in the USA, do not agree and place this jelly fungus in the genus Myxarium.

Exidia, the generic name, means exuding or staining, and both terms seem appropriate because these jelly fungi do look like exudations when moist and like dark stains on wood when they dry out.

The specific epithet nucleata comes from the Latin noun nucleatus, meaning a little nut or kernel; it is a reference to the opaque white nodular inclusions of calcium oxalate within the otherwise translucent and often largely transparent fruit bodies.

Synonyms

1. Tremella nucleata Schwein.

2. Naematelia nucleata (Schwein.) Fr.

3. Myxarium nucleatum (Schwein.) Wallr.

4. Tremella gemmata Lév.

5. Exidia gemmata (Lév.) Bourdot & Maire.

Photo sources:

Photo 1 - Author: Michel Langeveld (CC BY-SA 4.0)

Photo 2 - Author: Michel Langeveld (CC BY-SA 4.0)

Photo 3 - Author: Shirley Zundell (CC BY-SA 4.0)

Photo 4 - Author: David Badke (CC BY-SA 4.0)

Photo 5 - Author: James Lindsey (CC BY-SA 2.5)