Keeping your “eggs” in one basket

Cyanthus olla with “eggs”. Photo: Bob Baldock.

State Herbarium Hon. Research Associates Pam Catcheside and Bob Baldock report another cryptic and appealing fungus. It has appeared in the Botanic Gardens, this time amongst bark chips associated with recent plantings of pistachio saplings adjacent to the Old Tram Barn. A previous BLOG article described the coral fungus, Aseroe rubra Labill.

It is a birds nest fungus, easily passed over by the casual visitor to the gardens, but worth close inspection. Its Latin name, Cyathus olla (Batsch) Pers., literally means “cup” and “pot”. The bulk of the fungus occurs as cryptic, microscopic threads (the mycelium), infiltrating and busily dissolving the wood and bark chips for food. But the mature fruiting body is visible to the keen observer.

Cyanthus olla. Photo: Bob Baldock.

At first a ball-shaped structure forms. Then the membranous top tears to reveal a hollow interior with 8 to 10 grey-black “eggs” at the bottom of a fruiting body about 10 mm across which becomes goblet-shaped. The outside is grey-brown, covered with fine hairs at first, but it may later become smooth. Each “egg” is a spore packet a mere 3-5 mm by 1-2 mm, attached to the sides of the cup by fine elastic threads (unfortunately not visible in the images provided). At this minute scale, raindrops falling inside the “nest” have enough force to fling the “eggs” and their threads up and 1 m away from the fruiting body − a small-scale but violent dispersal mechanism! The elastic threads act like the boluses of South American gauchos and wrap around any available obstruction as the “eggs” land, securing them in place.

Cyanthus striatus. Photo: David Catcheside.

The fluted birds nest fungus, Cyathus striatus (Huds.) Willd., also appears occasionally on wood mulch in the Botanic Gardens. The cups are similar in size to those of C. olla but their outer surfaces are covered with brown, shaggy hairs, and the inner surfaces are grooved or fluted, hence the name striatus.

Other birds nest fungi, Nidularia and Crucibulum species, lack elastic threads and have their “eggs” embedded in mucilage, but like Cyathus, rely on raindrops for dispersal.