Fig. 31.—Fresh-water red algæ. A, Batrachospermum, × about 12. B, a branch of the same, × 150. C, Lemanea, natural size.
The commonest genera are Batrachospermum and Lemanea ([Fig. 31]).
CHAPTER VIII.
SUB-KINGDOM III.
Fungi.
The name “Fungi” has been given to a vast assemblage of plants, varying much among themselves, but on the whole of about the same structural rank as the algæ. Unlike the algæ, however, they are entirely destitute of chlorophyll, and in consequence are dependent upon organic matter for food, some being parasites (growing upon living organisms), others saprophytes (feeding on dead matter). Some of them show close resemblances in structure to certain algæ, and there is reason to believe that they are descended from forms that originally had chlorophyll; others are very different from any green plants, though more or less evidently related among themselves. Recognizing then these distinctions, we may make two divisions of the sub-kingdom: I. The Alga-Fungi (Phycomycetes), and II. The True Fungi (Mycomycetes).
Class I.—Phycomycetes.
These are fungi consisting of long, undivided, often branching tubular filaments, resembling quite closely those of Vaucheria or other Siphoneæ, but always destitute of any trace of chlorophyll. The simplest of these include the common moulds (Mucorini), one of which will serve to illustrate the characteristics of the order.
If a bit of fresh bread, slightly moistened, is kept under a bell jar or tumbler in a warm room, in the course of twenty-four hours or so it will be covered with a film of fine white threads, and a little later will produce a crop of little globular bodies mounted on upright stalks. These are at first white, but soon become black, and the filaments bearing them also grow dark-colored.
These are moulds, and have grown from spores that are in the atmosphere falling on the bread, which offers the proper conditions for their growth and multiplication.