Examples of local action are furnished by _Schinzia_, which forms gall-like swellings on the roots of rushes; _Gymnosporangium_, which induces excrescences on the stems of junipers, and numerous leaf-fungi (_Puccinia_, _Æcidium_, _Septoria_, etc.), which cause yellow, brown, or black spots on leaves, as well as by _Ustilago_, which attacks the anthers or the ovary of various plants, and so forth. In such cases the injury done by a few centres of infection is very slight, but prolonged action may bring into play secondary effects such as the gradual destruction of the cambium round a branch, when, of course, the effect of ringing results; or if the fungus becomes epidemic and myriads of leaf-spots are formed, the destruction of foliar tissue, gradual taxing of the assimilatory cells, etc., may end in rapid defoliation, and renewed attacks soon exhaust the plants and lead to sterility and death, as often occurs with Uredineae--_e.g._ the coffee leaf-disease. It is highly probable that such fungi are particularly exacting owing to their exhausting demands for compounds of potassium, phosphoric acid, and other bodies. Examples of virulent and rampant general action are afforded by finger and toe in turnips, etc., where the roots are invaded by _Plasmodiophora_, which induces hypertrophy and rotting of the roots; and by the damping off of seedlings, where the fungus _Pythium_ rapidly invades all parts of the seedlings and reduces them to a water-logged, putrefying mass; or the potato-disease, which is due to the rapid spread of _Phytophthora_ in the leaves and throughout the plant, which it blackens and rots in a few days.