The Pezizales or cup fungi, which are typically disk or cupshape, comprise an extensive group, and vary in size from forms scarcely visible to the naked eye to forms several inches in diameter. One genus, Peziza, has a smooth ascomata, regularly saucer-shaped or cup-shaped. The genus contains many species which are met with chiefly on decaying vegetable matter. The spore-sacs are situated on the upper surfaces of the cups, and the spores are ejected with such force and in such profusion that they form a cloud around the plant from which they are expelled.
Peziza aeruginosa is a stalked green form, and is interesting because it permeates the wood of oaks and beeches with its mycelium, and gives a rich green colour to the wood, which makes it valuable for the manufacture of the famous "Tunbridge ware." One may often find the wood affected when the fruit cups are not evident.
Peziza Willkommii produces on larch trees a disease known as the "larch canker," which shows itself as a sunken, blistered hole from which resin flows. This patch is formed because the mycelium of the fungus attacks and destroys the cambium or green layer which lies under the brown bark, and since this is the tissue which builds up the wood of the trees, the growth of wood in this part is prevented.
The fruits appear above the bark in the form of little cups, white outside and scarlet within. When branches bearing golden-yellow needles are seen among the fresh green shoots of a larch, prematurely giving to the tree an autumnal appearance, one may expect to find Peziza Willkommii at work.