This time, I have a special kind of fungus for you. This species is Geastrum triplex Jungh. from the Geastraceae Family. In German, this species is known as “Halskrausen-Erdstern”. The common English name of this fungus is “Collared Earthstar”, what is also the literally translation of the German name.
G. triplex is a larger fungus, whose mushrooms (the fruit bodies, which carry the spores) reach 6 to 10 centimeters in diameter. The above-ground mushrooms grow in stocks of two or three fruit bodies per stock.
G. triplex - habitus
The most distinctive feature of G. triplex (and the most other species from the Genus Geastrum) is the habitus of the mushrooms, which remind of tuber, which grow in a star-shaped rosette. These habitus is a result of the ripening. Young mushrooms are tuber-shaped, when they sprout from the ground. Basically, a mushroom of G. triplex consists of two different layers: the Exoperidium and the Endoperidium with the spores. During the ripening, the Exoperidium breaks up and forms a saucer-like pedestal for the smaller Endoperidium. Later, the Exoperidium tears up into star-shaped rays, which surround the Exoperidium. A stem is missing.
Ripening of a G. triplex mushroom: 1) intial phase; 2) medium phase
3) final phase (with spore erruption)
(exp = Exoperidium; end = Endoperidium (in 2) with cracks; in 3) star shaped;
s = spores; h = hyphae; o = ostiole; c = collar)
This process is typically for all fungi from the Genus Geastrum. In addition, the Endoperidium of G. triplex also flakes off at the base and form a kind of collar around the Endoperidium. This is also the reason for the name “Collard Earthstar”. However, this collar may be missing or be only very inconspicuous. This leads to confusion with other species of the same Genus. In the most cases, G. triplex is confused with the similar Geastrum sessile (Sow.) Pouz., which is much smaller and never has a kind of collar.
G. triplex - younger mushroom in phase 2
As I said it before, the spores are inside the Endoperidium and leave it after ripening by the large pore at the the top of the mushroom (in Mycology: Ostiole). This eject often happens by an abrupt eruption. The spores are spherical and between 3 and 4 micrometers in diameter. They are also covered with some warts.
G. triplex - two mushrooms in phase three; the
ostiole and the collar are visible
G. triplex isn't poisonous. However, the whole fungus is completely uneatable, because the tissue is tough and has no taste.
G. triplex is a cosmopolitan and can be found all over the world (e. g. in Europe, North America South Africa etc.). It's a saprobe and thrives on dead, organic matter, from which it gets its nutrients by decomposing. Normally, this species can be found in deciduous forests on lime in the undergrowth or along rotten trunks and tree stumps. However, it can also be found sometimes in parks or bushes with a high entry of organic matter. I found this fungi on the campus of the Ruhr-University in Bochum, Western Germany.