British distribution: Widespread but rare.
Imagine a cup fungus, in which the stalk has elongated upwards to push the cup inside out. This is what has happened here. The fruitbody is an apothecium, but what would have been the inner surface of the cup is now the exterior of the upper part of the fruitbody. The yellow portion, therefore, is the hymenium.
The margins of the cup are not completely fused with the stem, but are still separated from it by a distinct groove. This is one feature by which Heyderia differs from Mitrula, a genus that used to be considered as including Heyderia species.
H. abietis is a decomposer of dead spruce (Picea) needles, its occurrence on needles of other conifers being much less certain. It is, then, a fungus of spruce plantations, in which it can occur in extraordinary quantity, its mycelium binding the surface layers of the litter. It is not at all common in Britain, but may be overlooked due to its apparent preference for younger plantations that can be difficult to explore.