The Trees of Texas 19 
different parts of its range. The scientific name of a plant is 
given to it by the individual who first describes the species, and 
the name of the species is usually followed by the name of the 
man who described it. For example, Quercus alba L. means 
that this plant was originally described by Linnaeus and given 
the name Quercus alba. No other plant is known by this name. 
Scientific names should be used more extensively by all in desig- 
nating plants, for it is only through this means that we are able 
to know with certainty that reference is made to a definite 
species. The name of a plant consists, usually, of two parts or 
words, as, for example, Prosopis glandulosa, Pinus palustris, 
Ulmus Americana, Quercus nigra. The first of these words indi- 
eates the genus to which the plant belongs, and is always capi- 
talized, the second indicates the species and is only rarely capt- 
talized. 
The classification of plants is an attempt to express their 
actual kinship, or what we are accustomed to know as blood re 
lationship. Each kind of plant is known as a species. A species 
consists of a group of individuals which resemble each other 
more than they resembleany other individual. For example, al! 
of the trees which we call Ulmus Americana are more like each 
other than they are like any other group of trees. Then there are 
eroups of species which are more like each other than they are 
hke any other species. Such a group is known as a genus. 
There are in our area four species, all of which are more like 
Ulmus Americana than they are like any other species, but each 
differs from it and from each other in certain essential character- 
istics. These species are Ulmus Americana, Ulmus alata, Ulmus 
erassifolia and Ulmus fulva. The name of the species consists 
of the generic name which denotes the genus, and is followed by 
the specific name which defines the species. But the genus and 
species is not the complete expression of the relatiom-hip of any 
given plant. There are groups of genera which resemble each 
other more closely than they resemble any other genera. Sueh 
groups are known as families; for example Ulmus (elms) and 
Celtis (hackberry) make up the family Ulmaceae. Families are 
likewise grouped into orders, and these.in turn into larger groups. 
It should be borne in mind that,. knowing the name by which 
a plant is designated marks only the beginning of an acquaint- 
