Litroduction. XV 
make this statement here simply for the purpose of warning 
beginners against depending too much upon descriptions, with- 
out collateral knowledge, and against being hasty in their 
decisions. It is hardly necessary to add that no person can 
expect to become acquainted with the names of plants by the 
use of books alone. There must be preliminary practical 
knowledge to render the study of botanical works profitable. 
As a rule we learn the names, and little more, of a great 
many plants, and we often go on loading our brains with these 
names until there is a break-down, because they are not asso- 
ciated with any peculiar characters possessed by their owners, but 
are simply based upon general appearance. Hence the need of a 
book of reference to refresh the memory, and assist in deter- 
mining the correct name of a plant. From what we have said 
respecting the variability of plants, it naturally follows that all 
descriptions are more or less comparative in their distinctions, 
that is to say, without having any particular standard or 
starting-point, we frequently employ the words small and 
large, and many other terms, in describing plants of this or 
that group, and therefore these terms are qualified to a certain 
extent by the general characteristics of the plants under con- 
sideration. It is far more hazardous to give dimensions with- 
out allowing a wide margin for variation, than to limit the 
description to distinguishing characteristics and relative size, 
hairiness, etc. This course has been followed to a great extent 
in the present work, and it is confidently believed that it will 
meet with approval, and be of more service than disconnected, 
though more complete descriptions. 
Botanical and Horticultural Nomenclature —With regard 
to the nomenclature of plants, we have endeavoured to select 
the names sanctioned by recognised authorities; and in cases 
where plants are more generally known under erroneous appel- 
lations, these are given. In many instances plants possess 
two or more names. This may have proceeded from different 
botanists having published descriptions of the same plants 
unknown to each other, or it may rest upon the views enter- 
tained respecting the definition of a genus or species. Often- 
times, however, the advance of knowledge has rendered it 
necessary or desirable to change the name of a plant. Familiar 
