April, 1909.] 
The Classification of Plants, V. 
489 
THE CLASSIFICATION OF PLANTS, V. 
John* H. Schaffner. 
In a previous paper the entire plant kingdom was classified 
into seven fundamental divisions or subkingdoms, representing 
the great successive stages in the evolution of plants as a whole. 
These groups do not show genetic relationships but simply steps 
in the upward evolutionary motion. But there is a principle of 
segregation operative in the organic kingdom as well as one of 
progression. The whole plant kingdom thus comes to be a series 
of greater and smaller divergent lines or branches. In a group 
of nonsexual organisms every line of descent is a single line which 
diverges from another line at a definite point, but in a sexual 
group, where interbreeding goes on freely, there is an interaction 
throughout the whole mass and the scheme of descent resembles 
an elongated net with greater and smaller meshes. The whole 
progressive network of descent of a group may, however, also be 
represented by a line. When individuals or groups of individ¬ 
uals arise which become sterile to other members of the general 
group a new line is segregated, so that for the larger groups the 
diagram of descent must be quite similar whether of sexual or 
nonsexual forms, even though the diagram for individuals is 
fundamentally different in the two cases. 
As a convenient guide to memory, the scheme of relationships 
may be represented graphically by a tree with greater and 
smaller branches. Every branch thus recognized, whether large 
or small, is characterized by some peculiarity which remains 
dominant in all of the individuals and groups of the branch. Or 
in other words, as Bessey* has said: “Every phylum is the 
result of a development which differs from that which preceded 
it because of the incoming of a new dominant idea.’’ The number 
of great branches or phyla recognized depends somewhat on the 
views of the particular systematist making the classification. It 
is not always easy to distinguish fundamental genetic characters 
from those which are merely progressive, and may be developed 
in various unrelated groups. Among the characters which do 
not represent genetic relationships, when considered by them¬ 
selves, but which have been developed independently in various 
lines may be mentioned the following: Origin of sexuality, dif¬ 
ferentiation of gametes, passage from a unicellular to a filamen¬ 
tous condition, differentiation of the filament with base and 
apex, loss of chlorophyll with development of parasitism and 
saprophytism, development of unisexual gametophytes, loss of 
sexuality, origin of heterospory, development of complex leaf 
* Bkssev, Cii \m.rs E. The Phyletic Itiea in Taxonomy. Science N. S. 29: 91-100, 1909. 
