--Marine red seaweeds. _A_, _Dasya_. _B_,
_Rhodymenia_ (with smaller algae attached). _C_, _Grinnellia_. _D_,
_Delesseria_. _A_, _B_, natural size; the others reduced one-half.]

The fresh-water forms are not common, but may occasionally be met with
in mill streams and other running water, attached to stones and
woodwork, but are much inferior in size and beauty to the marine
species. The red color is not so pronounced, and they are, as a rule,
somewhat dull colored.

[Illustration: FIG. 31.--Fresh-water red algae. _A_, _Batrachospermum_,
x about 12. _B_, a branch of the same, x 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 algae. Unlike the algae, 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 algae, 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
_Siphoneae_, 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