rments, bacteria, and the like, many of them
very destructive to other vegetable and to animal life, are also low
forms of the class of Fungi.[1]

[Illustration: Fig. 587. Ascophora, the Bread-Mould. 588. Aspergillus
glaucus, the mould of cheese, but common on mouldy vegetables. 589. A
species of Botrytis. All magnified.]

FOOTNOTES:

[1] The "Introduction to Cryptogamous Botany," or third volume of "The
Botanical Text Book," now in preparation by the author's colleague,
Professor Farlow, will be the proper guide in the study of the
Flowerless Plants, especially of the Algae and Fungi.

SECTION XVIII. CLASSIFICATION AND NOMENCLATURE.

519. Classification, in botany, is the consideration of plants in
respect to their kinds and relationships. Some system of Nomenclature,
or naming, is necessary for fixing and expressing botanical knowledge so
as to make it available. The vast multiplicity of plants and the various
degrees of their relationship imperatively require order and system, not
only as to _names_ for designating the kinds of plants, but also as to
_terms_ for defining their differences. Nomenclature is concerned with
the names of plants. Terminology supplies names of organs or parts, and
terms to designate their differences.

Sec. 1. KINDS AND RELATIONSHIP.

520. Plants and animals have two great peculiarities: 1st, they form
themselves; and 2d, they multiply themselves. They reproduce their kind
in a continued succession of

521. =Individuals.= Mineral things occur as _masses_, which are
divisible into smaller and still smaller ones without alteration of
properties. But organic things (vegetables and animals) exist as
_individual beings_. Each owes its existence to a parent, and produces
similar individuals in its turn. So each individual is a link of a
chain; and to this chain the natural-historian applies the name of

522. =Species.= All the descendants from the same stock therefore
compose one species. And it was from our observing that the several
sorts of plants or animals steadily reproduce themselves, or, in other
words, keep up a succession of similar individuals, that the idea of
species originated. There are few species, however, in which man has
actually observed the succession for many generations. It could seldom
be proved that all the White Pine trees or White Oaks of any forest came
from the same stock. But observation having familiarized us with the
general fact that individ