With the growth of lichen edges often occurs destruction and death of older portions, whereby individual splits into a number of separate plants. Sor

Reproductive structures of lichens (soredia and isidia) [vegetative, propagation]

With the growth of lichen edges often occurs destruction and death of older portions, whereby individual splits into a number of separate plants.

Soredia and isidia are special reproductive structures of lichens as a single integrated organism.

Soredia

The most common method of lichen reproduction should consider the development of very small budlike outgrowths (soredia) on the upper surface of the thallus. Soredium consists of one or more cells of algae, surrounded by a small number of the hyphae (diagram 295, 1). Hypha begins to branch out of algae layer, its branch covers one, two or more algae cells, and formed this way soredia pushes out.

If soredia falls on a suitable substrate and finds conditions favorable for its growth, it begins to develop itself in the thallus. Taken from http://worldofschool.org

Diagram 295. Soredia, isidia and the development of the thallus in lichens: 1. Cut of thallus with soredia. 2. Isidia. 3. Development of the lichen thallus from germinating fungal spores and algae: 1 — the initial stage; 2 — a more advanced stage; fs — fungal spores, a — algae grams, h — hyphae

Isidia

In some lichen on thalli form the so-called isidia — special outgrowths, which have algae and pieces, fragments of fungal hyphae. They are covered with the cortical layer (diagram 295, 2). Isidia are fragile, easily break off and when fall on the substrate, give rise to new lichen thalli. Isidia are rarer than soredia. For example isidia are in Evernia furfuracea, growing on the bark of pine trees, on the upper side of its thallus