Bird's-Nest Fungus

Wayne's Word Index Noteworthy Plants Trivia Lemnaceae Biology 101 Botany Scenic Wildflowers Trains Spiders & Insects Search
  Wayne's Word Noteworthy Plant  
Originally Published In 1996

Bird's-Nest Fungus Update

A Minute Fungus With A Remarkable
Method Of Dispersing Its Spores

W.P. Armstrong Updated 4 November 2021

This issue of "Noteworthy Plants" is dedicated to a tiny cup-shaped fungus containing minute flattened spheres resembling eggs in a bird's nest. It is the reproductive or fruiting body of a remarkable fungus known in scientific circles as Cyathus olla.

This unusual species belongs to the order Nidulariales (Class Basidiomycetes), a fascinating group of fungi appropriately named "bird-nest fungi." The little cups are about five millimeters in diameter, about half the size of an ordinary thumb tack. They appear during the late winter and early spring rainy season along a trail on the hillside east of the main Palomar College campus. The trail starts at a lovely creek lined with white alders and ascends a north-facing slope of dense coastal sage scrub where it connects with the upper part of the Palomar College Arboretum. Like the chaparral, this endangered California plant community receives its rainfall during the winter and spring, primarily in the months of January through April. The little cups only appear during this season when the soil is damp, particularly in shady places along the trail. They are not conspicuous and are easily overlooked by joggers and casual observers. This is yet another example of an inconspicuous species that lives out its life in a marvelous and unique cycle that is seldom seen by people.

Several fruiting bodies (splash cups) of the amazing bird's-nest fungus (Cyathus olla) growing along a trail through the Coastal Sage Scrub northeast of the Palomar College campus. The small size of these fungi (not their value) is indicated by the U.S. penny (one cent).

  How Large Is Penny In Above Image  

The cup-shaped fruiting body of Cyathus olla contains 4-5 or more "eggs." The eggs are flattened lentil-shaped structures called peridioles and they contain special cells called basidiospores by which this fungus reproduces and disperses itself. Each peridiole is attached to the inner surface of the cup by a slender, hollow stalk which contains an inner, coiled, threadlike, funicular cord. The fragile outer layer of the stalk (called the purse) is easily ruptured, thus releasing the inner, coiled, funicular cord. When wet, the funicular cord elongates greatly and may reach a length of 6-8 inches (15-20 cm). The base of this elongated cord (called the hapteron) is very sticky and adheres readily to solid objects after it is released from the cup.

Bird's-nest fungus (Cyathus olla). This specimen was growing in a flower pot with Brodiaea terrestris ssp kernensis collected from the Laguna Mountains of San Diego County.

Bird's-nest fungus (Cyathus olla) on the campus of Palomar College.

Cups of Cyathus essentially serve as "splash-cups" during a rain storm. Similar splash cups containing small asexual "buds" called gemmae are also found on the thallus of certain liverworts such as species of Marchantia. Rain drops falling at approximately six meters per second strike the cup and eject the peridioles to a distance of three to four feet. [In the related genus Sphaerobolus, the single peridiole in each cup is forcibly ejected by an internal osmotic pressure build-up, like a miniature cannonball shot from a funnel-shaped blunderbuss muzzle.] Even though it is only rain drops falling on the cup of Cyathus, the force of the ejection causes the fragile outer portion of the stalk (called the purse) to burst--thus releasing the inner funicular cord and basal hapteron that were coiled up inside the hollow stalk. Like a wad of glue, the sticky hapteron strikes a solid object, such as a nearby plant, adheres to a branch, and as the peridiole continues in flight the funicular cord expands to its full length. Then, like a tetherball winding around a pole, the peridiole winds around the branch where the hapteron has become attached. Thus, the peridiole soon hangs down vertically or is wound around the object to which the hapteron is attached. Upon drying, the peridiole splits open releasing its precious cargo of spores which fall to the ground--perhaps being carried by the wind to new substrates.

A longitudinal section through the fruiting body of Cyathus olla
showing 5 peridioles attached inside the funnel-shaped peridium.

When a peridiole is ejected by a raindrop, the basal purse is torn at its lower end, releasing the coiled funicular cord which bears a sticky hapteron at its end. Like a wad of glue, the sticky hapteron strikes a solid object, such as a nearby plant, adheres to a branch, and as the peridiole continues in flight the funicular cord expands to its full length. Then, like a tetherball winding around a pole, the peridiole winds around the branch where the hapteron has become attached. For more information see the fascinating article by H.J. Brodie (1951): "The Splash-Cup Dispersal Mechanism In Plants," Canadian Journal of Botany Vol. 29: 224-234. [Illustration by Elaine M. Collins, Palomar College; modified from Canadian Journal of Botany 29: 224-234, 1951.]

Bird's-Nest Fungus (Cyathus olla)

Another Species Of Bird's-Nest Fungus Found At Wayne's Word

When I first saw these small brown balls in my Camelia Garden I thought they were rabbit droppings. After searching for their ID, I finally realized they are a different species of bird's-nest fungus (Cyathus striatus). This species is easily recognized by radiating striations (flutted ridges) on the inner cup (peridium). See following image.

Bird's-Nest Fungus (Cyathus striatus) showing immature & mature (opened cup) with
conspicuous striated peridium. Scroll down for more images of this remarkable fungus.

The Transformation Of Little Fungus Balls Into Bird Nests!

Why Is This Species Called: Fluted Bird's-Nest Fungus?

Concluding Remarks About This Remarkable Fungus Life Cycle:
Bird's-nest fungi belong to the fungal family Nidulariaceae. Members of this family contain both haploid and diploid stages, typical of the fungal division Basidiomycota in the kingdom Fungi, Domain Eukarya. Like other wood-decay fungi, this life cycle may be considered as two functionally different phases: the vegetative stage for the spread of mycelia, and the reproductive stage for the establishment of spore-producing structures, the fruiting bodies. These are the cup-shaped structures (peridia) resembling a bird's nest containing spore-bearing peridoles resembling tiny, flattened (lenticular) eggs.

Sexual Phase: Starting with spores dispersed from peridioles.

Haploid basidiospores germinate under optimal conditions of moisture and temperature, and grow into filaments called hyphae, penetrating leaf litter and decaying wood like roots. These hyphae are uninucleate (each cell containing a single nucleus). The growing tips expand and spread into a branched network called the mycelium. When two hyphae of different mating types fuse with one another (a process called plasmogamy), they produce binucleate (dikaryotyic) hyphae, each cell with 2 nuclei, from each mating type.

After a period of time and under the appropriate environmental conditions, the dikaryotic mycelia may enter the reproductive stage of the life cycle. Fruiting body formation is influenced by external factors such as season (which affects temperature and air humidity), nutrients and light. As fruiting bodies develop they maintain binucleate cells by a remarkable method called "clamp connections" typical of other basidiomycetes, such as mushrooms. Eventually the typical cup-shaped peridium is produced, with small peridioles, each containing the basidia upon which new basidiospores are made. Young basidia contain a pair of haploid sexually compatible nuclei which fuse, and the resulting diploid fusion nucleus undergoes meiosis to produce basidiospores, each containing a single haploid nucleus. The dikaryotic mycelia from which the fruiting bodies are produced is long-lasting, and will continue to produce successive generations of fruiting bodies as long as the environmental conditions are favorable.

Spore Dispersal:

The nests are "splash-cups." When a raindrop hits one at the right angle, the walls are shaped such that the peridioles are expelled to about 1 m away from the cup in some species. The peridioles have a trailing funicular cord, with a sticky hapteron at one end. If the glue-like hapteron attaches to a twig on its flight, the funicular cord will swing around and wrap itself around the twig, like a tether ball winding around a pole. The peridioles split open to release the fungal spores. Small animals can also eat the spore-filled peridioles to disperse the spores after they pass through the digestive tract.

  Compare With Gill Fungus Life Cycle: Start With Basidiospore (n)  

Return To WAYNE'S WORD Home Page
Go To Biology GEE WHIZ TRIVIA Page