Figure 3. A pair of immature Nidula candida showing characteristic external nest features and lids that protect the developing eggs. Renée Lebeuf photo.
considerations in identifying species. Te openings of young nests in
Nidula, Crucibulum and Cyathus are covered by a veil-like membrane called the epiphragm that often matches the exterior nest walls in texture and color (Fig. 3). Tese lids act like veils and protect immature eggs from mycophages and from being prematurely ejected from the nests. With time, the hairs disappear leaving the membranes white and the BNF temporarily more visible. As the nests’ mouths widen, the epiphragms rupture and disappear revealing the mature eggs below (Fig. 1) (Brodie, 1975). Variations within any given fungal
species are common and BNF are no exception. Years ago, some variants were mistakenly named as new species. Today, they are recognized simply as intraspecific differences caused by genetics or by environmental factors such as light and moisture that can vary from habitat to habitat (Brodie, 1975). Common intraspecific differences include the color, size and shape of nests
10 FUNGI Volume 19:2 Summer 2026
and the number of eggs. When identifying species, it helps
to use descriptions that include ranges for these features. Nest “irregularities” are common too. One irregularity in C. laeve, for example, is “twinning” which occurs when two adjacent nests share a section of wall or basal stem (Fig. 4). Brodie suggests that twinning happens at the primordia stage when “knots” on a mycelia merge. Another irregularity is “regeneration” in which a new fruiting body grows within the remains of an old nest (Brodie, 1975). While not diagnostically important in distinguishing species, these curiosities add interest to the study of the mushrooms. Bird’s Nest Fungi eggs or peridioles
(Fig. 4) are lentil-shaped, although they may appear somewhat angular in crowded nests. Individually, they measure 5 mm or less in diameter and have a thin leathery, or gelatinous outer layer. Egg color varies from colorless to creamy, black, gray, or brown depending on the species (Fig. 4 and Figs. 6–10). Mature eggs contain a gleba, a complex
inner mass of spores and basidia intermingled with sterile hyphae typical of gasteroid fungi like puffballs and stinkhorns. Te eggs are often neatly arranged in a single layer or multiple layers. Most Crucibulum and Cyathus nests have between 5 and 8 eggs but 15 or more are not unusual. In Nidularia, which have large globose nests, eggs can number around a hundred. Te eggs develop at different rates depending on the species. In Crucibulum, they mature simultaneously. In Cyathus striatus, they mature gradually from the top down while in Cyathus olla they mature from the bottom up. A single egg can contain around thirty million spores. Once dispersed from the nests, the eggs are not replaced, so empty nests are common finds at season’s end (Brodie, 1975; Hassett, et al., 2015). Some BNF genera have unique features
at the base of each egg. In Cyathus and Crucibulum, each peridiole bears a short stalk called the purse, which attaches firmly to the inner wall of the egg (Fig. 2). Te purse connects to a second stalk,
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