292 INTRODUCTION 
of the divisions end in -phyta, commonly written -phyte, from 
the Greek word phyton which means plant. The names of classes 
commonly end in -tneae or -eae and are usually derived from some 
important group included. Thus the Lycopodineae is the class 
containing the Lycopods, and the Filicineae is the class contain- 
ing the Ferns. 
The names of orders end in -ales, and orders are commonly 
named from some prominent family included. Thus the Rosales 
are named from the Rosaceae, the Rose family. Names of families 
usually end in -aceae and are commonly derived from some 
prominent genus, as for example the Liliaceae, which is the Lily 
family. The names of genera are Latin nouns in the nominative 
case. Thus Quercus is the Oak genus, Pyrus, the Apple genus, 
and Acer, the Maple genus. Species have two names, the name 
of the genus and the name that distinguishes the species. For 
example, Quercus alba is the White Oak, while Quercus rubra is 
the Red Oak. Quercus is the name of the genus, and the terms 
alba (the Latin term for white) and rubra (the Latin term for red) 
name the species. In English we simply change the terms about 
and say White Oak instead of Oak White. 
The Divisions of the Plant Kingdom. — The phylogenetic 
divisions of the Plant Kingdom arranged in phylogenetic 
order are Thallophytes, Bryophytes, Pteridophytes, and Spermato- 
phytes. 
The Thallophytes are the simplest plants and are regarded as 
the lowest and most primitive from the standpoint of evolution. 
The word means thallus plants. As previously stated the 
ending -phyte always means plant. Thallus refers to the fact 
that the plant body has a simple organization. It is not differen- 
tiated into roots, stem, and leaves. Bacteria, Toadstools, and 
Algae are familiar Thallophytes. The plant body of some of 
them consists of a single cell, which is the simplest plant body 
possible. 
The Bryophytes are so named because they are chiefly Moss 
plants. Besides the Mosses, they also include the Liverworts. 
The Bryophytes have better organized plant bodies than the 
Thallophytes and are, therefore, considered higher in the scale 
of evolution. 
The Pteridophytes are so named because they include the Fern 
plants. Most Pteridophytes are Ferns, but this group includes 
