The yeast plant and its allies are saprophytes and form no chlorophyll.
These they obtain usually in the form of carbohydrates from the dead remains of other organisms, or in this or other forms from the living cells of their hosts; in the former case they are termed saprophytes, in the latter parasites.
Most genera are saprophytes, but some - Chaetocladium, Piptocephalis - are parasites on other Mucorini, and one or two are associated casually with the rotting of tomatoes and other fruits, bulbs, &c., the fleshy parts of which are rapidly destroyed if once the hyphae gain entrance.
Some fungi, though able to live as saprophytes, occasionally enter the body of living plants, and are thus termed facultative parasites.
An epiphytic fungus is not necessarily a parasite, however, as many saprophytes (moulds, &c.) germinate and develop a loose mycelium on living leaves, but only enter and destroy the tissues after the leaf has fallen; in some cases, however, these saprophytic epiphytes can do harm by intercepting light and air from the leaf (Fumago, &c.), and such cases make it difficult to draw the line between saprophytism and parasitism.
In parasites (Lathraea, Orobanche) and in plants growing on decaying vegetable matter (saprophytes), in which no chlorophyll is formed, these scales are the only leaves produced.
Schizomycetes are ubiquitous as saprophytes in still ponds and ditches, in running streams and rivers, and in the sea, and especially in drains, bogs, refuse heaps, and in the soil, and wherever organic infusions are allowed to stand for a short time.
Fischer has proposed that the old division into saprophytes and parasites should be replaced by one which takes into account other peculiarities in the mode of nutrition of bacteria.
The vast majority of bacteria, on the other hand, which are ordinarily termed saprophytes, are saprogenic, i.e.
Similarly we are unable to divide Schizomycetes sharply into parasites and saprophytes, since it is well proved that a number of species - facultative parasites - can become one or the other according to circumstances.