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Hemitrichia calyculata

The mustard-yellow fruitbodies of Hemitrichia calyculata are only a few millimetres tall. As the sporangia mature, the outer wall (= peridium) breaks away and the internal mass (capillitium and spores) flounces out like cotton candy and forms a top-shaped head. The heads sits in a shallow cup (= calyculus) that is a persistent remnant of the peridium. The support stalk is short and blackish. This species is very common throughout our region. The sporangia are produced on logs or stumps in hundreds. When very young, they are a brilliant vermillion to cinnabar colour and are easily spotted. Hemitrichia clavata is very similar but the basal cup (= calyculus ) is much deeper and the fruitbodies are thinner and club-shaped to pear-shaped rather than top-shaped.

In all species of Hemitrichia the threads of the capillitium are marked with spiral thickenings along their length. As with Arcyria, changes in relative humidity cause moisture to be taken up or lost by the threads and this results in changes in tension along the length of the threads. Adjustments to these tensions causes the threads to wriggle and eject the spores for dispersal by the wind.