Saprophytic Plants are plants that feed upon decaying organic matter. In common with many of the Parasitic Plants (q.v.), which are plants that live on or in and at the expense of other organisms, they are often devoid of chlorophyll. The reason of this peculiarity is obvious. Chlorophyll being the material used by ordinary plants for the decomposition of the carbonic acid of the air in order that they may retain the carbon, and with it build up all the carbon compounds characteristic of organic nature (see VEGETABLE PHYSIOLOGY), it is plain that those plants which in virtue of a saprophytic or a completely parasitic habit obtain their carbon compounds ready-made up to a certain point do not require a special mechanism of green stuff to manufacture those compounds. If the saprophytism be not complete or 'pure' there will be at least some chlorophyll remaining, as in the flowering axis of the orchid Neottia. Saprophytes may obtain their nourishment and especially their carbon compounds either from the remains of dead organisms or from organic compounds formed by living organisms. The fungi that live upon the bark of trees and the leaf-soil of forests and meadows (e.g. mushrooms) are examples of the former case; those that feed upon the juice of fruits and sugary solutions (e.g. moulds and yeasts) of the latter case. Examples of saprophytes are found in the Phanerogams, the Fungi, and the Bacteria. Among the Phanerogams are some common native Orchids—Neottia, Corallorhiza, Lattrea, and Monotropa. After prolonged nourishment within the loose humus such plants send up flowering shoots above the surface.
Fungi (q.v.) may be physiologically classified as parasites and saprophytes; but this classification does not coincide with a morphological one. Further, there are certain species which lie between the two extremes, and these may be described as parasites which may become wholly or in part saprophytic, through the whole course of their development or during certain stages of it; and also there are saprophytes which, with the same variations, may become parasitic. Hence the complete physiological classification of the Fungi becomes (1) Pure saprophytes; (2) 'Facultative' saprophytes—i.e. parasites which become saprophytic; (3) 'Obligate' parasites—i.e. species to which the parasitic life is indispensable; (4) 'Facultative' parasites.
The external conditions necessary for the commencement of germination of Fungi are the same as those needful to the germs and seeds of other plants: they are a certain temperature, a supply of oxygen and of water, in certain cases a supply of nutrient substances. The spores of the Perenosporæ and of the Uredineæ germinate on drops of pure water; nutrient solutions may even be a hindrance. The Mucorini, on the other hand, emit only rudimentary germ-tubes in pure water; they require a nutrient solution for germination. Most Fungi vary towards one extreme or other according to the species.
A further characteristic of many Fungi is that certain species are only to be found upon a specific substratum. For instance, the Saccharomycetes, which excite alcoholic fermentation, appear on fruits only when these are ripe, and in the winter are found in soil around those plants whose ripe fruit they attack, and very rarely in any other place. Further, the effect upon the substratum varies with the species to a greater or less extent. On the other hand, many diverse species live on the same substratum and effect the same results upon it—e.g. many species of Saccharomycetes and certain species of Mucar produce very similar fermentations in saccharine fluids (see FERMENTATION). A destructive effect is witnessed in the reduction of timber to a mass of dirt by Merulius lacrymans.
Bacteria (q.v.) may be classified physiologically in the same terms as the Fungi. And their functions vary in the same way. Many oxidise their substratum; the Micrococcus of vinegar oxidises ethyl-alcohol into acetic acid, and by further combustion into carbonic acid and water. Others excite characteristic fermentations, lactic acid, butyric acid fermentations, &c., produced by specific organisms. Others incite Putrefaction (q.v.).
For further information, see Goebel's Outlines of Classification and Special Morphology; De Bary's Morphology of the Fungi, Mycetozoa and Bacteria; Sachs's Physiology of Plants; Vines's Physiology of Plants; and the literature referred to in these works.