Haemmatoma persoonii

Asci of this lichen are clavate or club-shaped. In this photo they have been stained with potassium iodide which explains their blue coloration. The asci of some lichens will not stain with this method while others, (some Arthonia species, for example,) will stain red. In many lichens the color pattern assumed by a stained ascus, especially the tip, can be used in identifying the genus. With this method the asci are normally pretreated with potassium hydroxide before the addition of potassium iodide.