# Crucibulum
**Crucibulum** (Tul. & C. Tul.) is a small genus of bird's nest fungi in the order [Agaricales](https://www.edgepedia.org/agaricales), characterized by urn-shaped fruiting bodies a few millimeters across that contain lens-shaped spore packets called peridioles, which are dispersed by falling raindrops. The type and, according to one current treatment, the only species recognized in the genus worldwide is *Crucibulum laeve* (Huds.) Kambly, the common bird's nest or white-egg bird's nest fungus.[1](https://fungalguide.landcareresearch.co.nz/webforms/FG_Group.aspx?Group=Birdsnest) • [2](https://myco-lb.jgi.doe.gov/Crula1/Crula1.home.html)
| Key fact | Detail |
|---|---|
| Type species | *Crucibulum laeve* (Huds.) Kambly, originally described as *Peziza laevis* by William Hudson in 1778 and transferred to *Crucibulum* by P. E. Kambly in 1936[3](https://www.first-nature.com/fungi/crucibulum-laeve.php) |
| Fruitbody | Short cylindrical, woolly-textured dark brownish gray outside and smooth and yellowish inside; typically 5 to 10 mm across and up to 10 mm tall[1](https://fungalguide.landcareresearch.co.nz/webforms/FG_Group.aspx?Group=Birdsnest) • [3](https://www.first-nature.com/fungi/crucibulum-laeve.php) |
| Peridioles | Five to eight whitish "eggs" per nest, each about 1.5 mm in diameter, attached to the nest base by a fine elastic cord[1](https://fungalguide.landcareresearch.co.nz/webforms/FG_Group.aspx?Group=Birdsnest) • [3](https://www.first-nature.com/fungi/crucibulum-laeve.php) |
| Spores | Ellipsoidal, smooth, 8-11 x 4-6 µm, inamyloid; spore mass white[3](https://www.first-nature.com/fungi/crucibulum-laeve.php) |
| Dispersal | Raindrops knock the peridioles out of the cup; they spring from the cups and adhere to surfaces three or four feet away[3](https://www.first-nature.com/fungi/crucibulum-laeve.php) • [4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest) |
| Habitat | Saprobic on decayed woody debris, fallen twigs, decaying vegetation, wood chips, and landscaping mulch[5](https://www.bioimages.org.uk/bioinfohtml/html/Crucibulum_laeve.htm) • [4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest) |
| Genome | Sequenced (strain CBS 166.37) as part of the 1000 Fungal Genomes Project[2](https://myco-lb.jgi.doe.gov/Crula1/Crula1.home.html) |
## Description
The fruitbody is a small, stemless cup. In *Crucibulum laeve* the inside of the cup is yellowish and smooth, with tiny whitish "eggs" within, while the outside is dark brownish gray and woolly-textured.[4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest) Young fruitbodies are yellow-brown tapering cups covered at the top by a yellowish woolly membrane (the epiphragm); at maturity this cover ruptures around the rim and falls away, exposing the peridioles to rain.[3](https://www.first-nature.com/fungi/crucibulum-laeve.php) Fruitbodies often occur in densely packed groups, and crowding from neighboring individuals can distort the nests.[3](https://www.first-nature.com/fungi/crucibulum-laeve.php)
Each peridiole is flattened and attached to the base of the nest by a very thin but strong cord, the funicular cord.[4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest) The peridioles contain the basidia and basidiospores.[2](https://myco-lb.jgi.doe.gov/Crula1/Crula1.home.html) The generic name *Crucibulum* means "in the form of a crucible", and the specific epithet *laeve* means smooth, referring to the smooth inner surfaces of the nests.[3](https://www.first-nature.com/fungi/crucibulum-laeve.php)
## Splash-cup dispersal
Bird's nest fungi use the kinetic energy of raindrops to launch their reproductive bodies. When a raindrop hits the peridioles in the cup, they spring out and adhere to nearby surfaces, in *C. laeve* landing three or four feet away.[4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest) This mechanism differs from that of puffballs such as *Lycoperdon* and *Bovista*, where raindrops release clouds of spores; in bird's nest fungi the peridiole is expelled as a whole.[2](https://myco-lb.jgi.doe.gov/Crula1/Crula1.home.html)
The attachment structures differ among the genera. During splash-cup dispersal, the peridiole of *Cyathus* adheres to vegetation through sticky hyphae at the end of its complex funicular cord, called a hapteron. *Crucibulum* has a simple funicular cord with little adhesion, but the peridiole surface itself is slightly adhesive, so fixation occurs through both structures together. In *Nidula* the peridioles are small, lack a funicular cord, and are themselves highly adhesive.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC10082518/) In some cases the spore sacs adhere to nearby vegetation and are eaten by herbivores; spores that pass through the digestive tract unscathed are deposited in droppings, which provide a suitable habitat and food source.[4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest)
## Ecology and distribution
*Crucibulum laeve* is saprobic, growing on fallen dead twigs, old rotting timber (including discarded plywood), decaying vegetation, wood chips, and landscaping mulch.[3](https://www.first-nature.com/fungi/crucibulum-laeve.php) • [4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest) British and Irish records confirm the fruitbodies as saprobes on decayed woody debris and decayed fallen twigs of broadleaved and coniferous trees.[5](https://www.bioimages.org.uk/bioinfohtml/html/Crucibulum_laeve.htm) Bird's nest fungi generally colonize dead woody materials, nutrient-rich soil, or dung, and wood-inhabiting species cause white rot on the colonized wood.[2](https://myco-lb.jgi.doe.gov/Crula1/Crula1.home.html)
The species is probably fairly common and widespread in Britain and Ireland but rarely reported because the fruitbodies are small and grow in dark, damp woodland; it also occurs throughout other temperate parts of the world, including mainland Europe, Asia, and many parts of North America.[3](https://www.first-nature.com/fungi/crucibulum-laeve.php) In Missouri it is found statewide, fruiting from July to October; in Britain and Ireland the season is also July to October.[4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest) • [3](https://www.first-nature.com/fungi/crucibulum-laeve.php) The fungus is not edible.[4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest)
## Taxonomy and phylogeny
The taxonomic history of *C. laeve* includes several synonyms, among them *Peziza laevis* Huds., *Cyathus crucibulum* Pers., *Nidularia crucibulum* Fr., and *Crucibulum vulgare* Tul. & C. Tul.; a revision of Persoon's herbarium notes that *Cyathus crucibulum* has been placed in a separate genus as *Crucibulum vulgare*, a synonym of *Crucibulum laeve*.[3](https://www.first-nature.com/fungi/crucibulum-laeve.php) • [7](https://repository.naturalis.nl/pub/531772/PERS1961001004005.pdf)
Family placement differs among references: British sources place *Crucibulum* in [Agaricaceae](https://www.edgepedia.org/agaricaceae) within Agaricales,[8](https://www.bioimages.org.uk/html/Crucibulum_laeve.htm) while North American field guides use [Nidulariaceae](https://www.edgepedia.org/nidulariaceae), the bird's nest fungi family.[4](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest) Molecular work supports the bird's nest fungi as a natural group: a 2021 multi-locus phylogeny (ITS, LSU, tef, and rpb2) by Nattapol Kraisitudomsook, Rosanne A. Healy, and Matthew E. Smith of the [University of Florida](https://www.edgepedia.org/university-of-florida) resolved Nidulariaceae as monophyletic, with Squamanitaceae as a potential sister taxon, and found that *Cyathus* and *Crucibulum* each formed their own independent, well-supported clade.[9](https://www.sciencedirect.com/science/article/pii/S1878614621000532) The family currently comprises six genera: *Cyathus*, *Crucibulum*, *Mycocalia*, *Nidula*, *Nidularia*, and *Retiperidiolia*.[10](https://pmc.ncbi.nlm.nih.gov/articles/PMC11290291/)
The deeper relationships remain unsettled. The 2021 study found the phylogenetic placement of *Crucibulum* unclear and the sister lineage of the family inconclusive.[9](https://www.sciencedirect.com/science/article/pii/S1878614621000532) A 2024 genome-scale analysis found a different arrangement, with *Cyathus* sister to the *Nidula*-*Nidularia* clade and *Crucibulum* sister to *Retiperidiolia reticulata*, and noted topological conflicts between analyses for the placement of some *Cyathus* and *Crucibulum* species.[11](https://munin.uit.no/bitstream/handle/10037/35790/article.pdf?isAllowed=y&sequence=3)
## Genome and research use
The genome of *Crucibulum laeve* strain CBS 166.37 has been sequenced as part of the 1000 Fungal Genomes Project. Because the family's unusual fruiting body morphology and rain-splash dispersal are distinctive within agaricoid fungi, the genome is intended to help unravel the evolutionary origins of this morphology; the lignocellulose-degrading enzymes of wood-inhabiting bird's nest fungi, which cause white rot, have been subject to intense research.[2](https://myco-lb.jgi.doe.gov/Crula1/Crula1.home.html)
## Similar names
The name *Crucibulum* is also used for an unrelated genus of marine gastropod molluscs (cup-and-saucer shells) established by Schumacher in 1817.[12](https://www.marinespecies.org/aphia.php?p=taxlist&tName=Crucibulum)
## References
1. [Crucibulum, Birds Nest fungi, Landcare Research Fungal Guide](https://fungalguide.landcareresearch.co.nz/webforms/FG_Group.aspx?Group=Birdsnest)
2. [Crucibulum laeve CBS 166.37 v1.0, JGI MycoCosm, 1000 Fungal Genomes Project](https://myco-lb.jgi.doe.gov/Crula1/Crula1.home.html)
3. [Crucibulum laeve, Common Bird's-nest Fungus, First Nature](https://www.first-nature.com/fungi/crucibulum-laeve.php)
4. [Splash Cup (Common Bird's Nest), Missouri Department of Conservation](https://mdc.mo.gov/discover-nature/field-guide/splash-cup-common-birds-nest)
5. [Crucibulum laeve host/saprobe relationships, BioImages](https://www.bioimages.org.uk/bioinfohtml/html/Crucibulum_laeve.htm)
6. [Rearranging the Bird's Nest Fungi: molecular review of internal clades in Cyathus, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC10082518/)
7. [Revision of the Nidulariaceae in Persoon's Herbarium, Rijksherbarium, Leiden](https://repository.naturalis.nl/pub/531772/PERS1961001004005.pdf)
8. [Crucibulum laeve taxonomic hierarchy, BioInfo/BioImages](https://www.bioimages.org.uk/html/Crucibulum_laeve.htm)
9. [Kraisitudomsook, Healy & Smith (2021). Molecular systematics and taxonomic overview of the bird's nest fungi (Nidulariaceae). Fungal Biology 125(9): 693-703.](https://www.sciencedirect.com/science/article/pii/S1878614621000532)
10. [Complete mitochondrial genome of the bird's nest fungus Nidula shingbaensis, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC11290291/)
11. [Molecular Phylogenetics and Evolution 193 (2024): 108010](https://munin.uit.no/bitstream/handle/10037/35790/article.pdf?isAllowed=y&sequence=3)
12. [Crucibulum taxon list, World Register of Marine Species](https://www.marinespecies.org/aphia.php?p=taxlist&tName=Crucibulum)
---
*Topic: Encyclopedia › Life and health › Microorganisms and fungi › Fungi and mycology › Basidiomycete taxa › Agaricomycetes › Gasteroid fungi › Stinkhorns and bird's-nest fungi › Nidulariaceae (bird's-nest fungi)*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license