SYSTEMATIC BOTANY. 175 
hot communicate any information regarding the other cha- 
_ racters, structure, or properties of the plant, and is of little 
or no use in the case of a new and unknown plant. 
629. Now, it has been found that, in the vegetable as in 
the animal kingdom, the species are grouped together by 
Nature in Classes or Families, differing from each other in 
several particulars, but in each of which families, all the spe- 
cies agree in some important and easily discernible charaec- 
ters, and, more or less, in their internal structure and pro- 
perties. These classes frequently run into each other, and 
their diagnostic characters and limits are not always so well 
marked as could be wished. Still, however, they are suffi- 
ciently distinct for the purpose of a good natural arrange- 
ment. Such a method, if at all perfect, should not only 
Serve the purpose of an artificial system, but enable us, in 
_the case of a new and unknown plant, from the examination 
of a few of its characters, to have an idea of many of its 
other characters, its internal structure, and habits, and to 
’ predict what properties it is most likely to possess. 
630. Many of these natural families must have been ob- 
served by every one who has paid even the slightest attention 
to plants. No one ever mistook the Mosses for the Grasses, 
or the latter for the Ferns, or these for the Lily tribe. Ac- 
_ cordingly, we find that there has always been some arrange- 
‘Ment in use, however imperfect. The ancients spoke of Trees, 
Shrubs, and Herbs, and this division is in popular use at the — 
Present time. Then, plants were considered with respect to 
their uses as food or as medicines, anid subdivided accord- 
ingly. Gradually, as our knowledge of plants increased, and 
the necessity for some arrangement became greater, they 
Were classified as Grasses, Cruciferous Plants, Bulbous 
Plants, &e. This division, however, which is on excellent 
Principles, the botanists of former times were unable to = 
tend to all plants, from their very limited knowledge of tail 
getable anatomy. To this circumstance also we must attri- 
bute the number of artificial systems which were invented to. 
Supply the place of a natural method. © Till the beginning of 
