XIX 
Besides these differences occasioned by accidental circumstances 
of growth, all plants are apt to exhibit permanent variations from 
the general form, due to the operation of more obscure causes; 
giving rise to what are termed varieties. These varieties are, in 
perennial plants, capable of propagation by subdivision of the root, 
or from slips or cuttings; but their seed usually reproduces the 
normal form, though it is yet a doubtful and disputed point 
whether they may not in some instances be permanently propa- 
gated by seed: they often diverge so greatly from the typical 
plant, that they are apt to be regarded by the ordinary observer 
as distinct, and even our most experienced botanists are sometimes 
unable to decide upon their real character. 
Among our native plants, the groups of Roses, Brambles, and 
Willows are remarkable instances of this obscurity regarding specific 
distinctions. Of upwards of seventy Willows figured and described 
in the present work, certainly not more than fourteen or fifteen can 
be satisfactorily distinguished as species. The twenty-four Roses 
are probably varieties of not more than five distinct plants; and 
the species of Rubus, which have been multiplied by some writers 
to a far greater extent than in this book, are perhaps referable 
to four specific types. The confusion naturally existing between 
species and varieties has been unfortunately greatly increased, by 
the anxiety of the students of local floras to extend the apparent 
field of their labours by the addition of new species,—an object 
more easily attained in a well-explored country by the subdivision 
of well-known groups, than by the discovery of really new plants, 
and a habit the more to be deplored, as it tends to destroy that sim- 
plicity of arrangement which is the only object of classification. 
Whether species have any definite limits in Nature, is a ques- 
tion foreign to the scope of the present work. As the term 1s 
applied in Botany, it may be generally defined as an assemblage 
of plants possessing a certain similarity in all essential points of 
structure, capable of being permanently propagated by seed, and 
d2 
