Astraeus hygrometricus

Morphological Features:

Basidiocarp globose in shape and 2 to 4 cm when closed; upon opening it can measure 6 to 8 cm and assumes a star-like form. The coloration of the fruiting body ranges from dirty white to brown, varying according to its distinct parts, which are described below.

Exopерidium, or the outer layer of the fruiting body. It consists of two well-differentiated layers: an outer brown layer that cracks and dries out easily, and an inner layer that is more matte, fleshy, and firm. Under humid climatic conditions, it opens into a star shape until it touches the ground; in dry weather, it contracts to protect the endoperidium.

Endoperidium, or the inner part of the fruiting body, is the structure that encloses the gleba where spores develop. It is globose in shape and measures approximately 3 cm in diameter; its color ranges from dirty white to brown, and it features an apical pore that allows for spore discharge.

Gleba, which also transitions from dirty white to darkish-brown tones as its spore mass matures.

Habitat:

Its most common fruiting season is autumn, although it may appear in other seasons. It shows no preference for a specific forest type; we have observed it beneath a wide variety of trees, typically on dry or sandy soils.

Observations:

This species is relatively easy to identify due to its tendency to contract during dry periods and expand with moisture. It may be confused with certain Geastrum species; however, all Geastrum species possess a columella. Nevertheless, it is true that some of them also exhibit hygroscopic behavior, albeit less pronounced.