XX11 INTRODUCTION. 



another in minor points, such as an irregular formation 

 of leaves or mode of growth, unusual colour of flowers, 

 extraordinary number of petals, &c., are termed varieties. 

 These words are frequently used loosely in common con- 

 versation, but the habit cannot be too carefully avoided 

 in botanical descriptions, as calculated to produce great 

 confusion. Throughout these pages they will be em- 

 ployed exclusively with the meanings above assigned, 

 which will be rendered clearer by the following exam- 

 ples : The wild sweet-scented Violet is called by botan- 

 ists Viola odordta ; the former name, Viola, indicating 

 that it belongs to the genus so called, and being, there- 

 fore, termed its generic name. Besides the scented 

 Violet, we have in England the Dog- Violet, the Marsh- 

 Violet, the Pansy, and several others, all belonging to 

 the same genus, and, therefore, described under the 

 name Viola. But the Dog- Violet differs from the 

 Sweet-scented, in having acute sepals, and leafy stems, 

 whereas the latter has blunt sepals, and the leaves 

 spring directly from the roots. The Dog- Violet is, 

 therefore, a distinct species, Viola camna. The Marsh- 

 Violet and Pansy differ also in important characters ; 

 they are, therefore, also considered distinct species, the 

 fact being indicated by the addition of the specific or 

 trivial 1 names, palustris and tricolor, to the generic name 

 Viola. The flowers of the scented Violet are sometimes 

 white and sometimes blue ; garden specimens are often 

 tinged with pink, and still more frequently, double. 

 These characters being either unimportant, or inconstant 

 for blue flowers generally have a great tendency to 

 sport to white, and double flowers are not perpetuated 

 by seed the blue, white, pink, and double sweet 

 Violets are not considered distinct species, but mere 



