TAXONOMY OR CLASSIFICATION 153 
thought to be closely related genetically. The species of 
a genus will show similarity in fundamental characters, 
such as the structure of the flowers and fruit, and usually 
also a similarity in habit, or general aspect. 
Familiar genera are the oaks, the pines, the asters, the golden- 
rods; or, among grasses, the blue-grasses and the wheat-grasses, the 
millets and the bromes. 
As genera do not exist in nature, but represent the 
taxonomist’s ideas as to groups of related species, botanists 
may not agree as to the limits of genera. The size of 
genera, that is, the number of species included, is some- 
times a matter of convenience. Conservative botanists 
would probably not recognize Panicum and Paspalum as 
separate genera, when considering the generic characters 
only, but each group contains such a large number of 
species that the two have been kept distinct for conve- 
nience. Some species are so different from their nearest 
allies that they cannot be consistently grouped with 
other species. Such a species stands as the sole rep- 
resentative of its genus, and the genus to which it belongs 
is called a monotypic genus. It not infrequently happens 
that after a monotypic genus is established other species 
are discovered, which are assigned to it, and it ceases to 
be monotypic. In contrast with monotypic genera are 
others, such as Panicum, Andropogon and Poa, with hun- 
dreds of species. Large genera may sometimes be con- 
veniently divided into smaller groups, such as subgenera 
and sections. 
From a nomenclatorial standpoint the term monotypic is used 
to indicate genera with only one species at the original place of 
publication. Cook suggests the word haplotypic for such genera. 
(Amer. Nat. 48:311. 1914.) 
