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Basidiomycota - Gasteromycetes

Puffballs, earthstars, bird's nest fungi, stinkhorns, and related fungi produce their spores inside the fruitbodies.  For this reason they are placed in the class Gasteromycetes (stomach fungi).  Members of this group are very variable in size and shape and have many interesting and novel ways of spreading their spores using wind, insects or rain.  Gasteromycetes range from the giant puffball (Calvatia gigantea) weighing many kilograms to the tiny Sphaerobolus stellatus which is only 2 mm across.

Puffballs and Earthstars

Puffballs are spherical, subspherical, ellipsoid, pestle-shaped or pear-shaped. The outer wall is usually roughened with spines that flake off to reveal a smooth membranous inner wall. The spores mature inside the fruitbody as a powdery mass. In the giant puffball, the outer wall cracks and breaks off as it dries out. This exposes the spore mass to the elements for dispersal.  In the small puffball (Lycoperdon) there is a well-defined pore at the apex.  Raindrops strike the outside wall of the spore sac and the implosion of the wall causes a puff of spores through the pore to the exterior for dispersal by the wind.

In the earthstars (Geastrum species ) a thick outer wall splits and the segments form a number of pointed arms.  As the fruitbody dries, the arms reflex to expose a puffball-like spore sac.  Earthstars form on the forest floor just below the loose duff. The reflexing arms raise the inner spore sac above the ground for better dispersal. Spores are puffed through a pore by raindrops in the same way as Lycoperdon.


In the young "egg "stage, stinkhorns resemble puffballs and their fruitbodies are spherical to subspherical or ellipsoid.  Their internal organization is more complex  (click here). Inside, there is an outer gelatinous layer surrounding an olive-green spore mass which covers the head of the stinkhorn.  In the eggs of Phallus and Mutinus, the head surrounds a central columella.  At maturity, the wall cracks open and the columella expands to form the support stalk. At this time, the gelatinous layer mixes with the spore mass to produce a fetid, evil-smelling, olive-green goo which also contains sugary materials.  The strong odour attracts flies from great distances to feed on the sweet, smelly stuff which sticks to their body parts and the spores are transported to other likely sites by the flies.

Bird's Nest Fungi

The fruitbody of a Bird's Nest Fungus (BNF) looks like a tiny nest with eggs (peridioles). The "eggs" are packages of thousands of spores contained within a hard outer wall (click here). In some BNF the eggs are anchored to the side wall by a structure that contains a long threadlike tail (funiculus) with a sticky base (hapteron). Falling raindrops causes mini explosions in the cone-shaped cups and the splash propels the eggs out of the cup. Eggs can be shot nearly two metres away from the cup and attach to a suitable substrate by means of the sticky base.

The "Big Bertha" of the fungal world is Sphaerobolus stellatus. Only 2 mm across, Sphaerobolus catapults its solitary, spherical egg (one mm in diameter) a distance of more than 6 metres (20 feet)!