XXXIV INTRODUCTION 



that most have broad-pointed leaves, broad blue petals with 

 numerous branched dark veins at their base, and a thick yellowish- 

 white spur ; but that some have the leaves drawn out into a longer 

 point, the petals narrower and more lilac, with few slightly- 

 branched veins, and a compressed dark-bluish spur. Some 

 botanists consider these two forms as distinct species, V. 

 Rivinidna and V. sylvestris, whilst others call them both varieties 

 of V, sylvestris, the first being then known as V. sylvestris, var. 

 Rivinidna, and the second as V. sylvestris, var. Reichenbachidna, 

 "var." being the abbreviation of the Latin " varietas." 



On the leaf-stalk of a Sweet-scented Violet or of a Wood 

 Violet we shall find two small narrow stipules ; but in the Pansy 

 we shall see that these are replaced by a pair that are large, leafy, 

 and pinnately-lobed. This is only one of the characters that 

 make us separate the Pansy as a distinct species, V. tricolor. 

 Sweet Violets, Wood Violets, Pansies, and in fact all other 

 Violets, though thus differing specifically, agree in having mono- 

 symmetric flowers with ear-like lobes (auricles) at the base of each 

 of their five sepals, a spur to the posterior petal, and five united 

 anthers with tail-like appendages from the base of two of them. 

 These, then, are the generic characters of the genus Viola. 

 According to the theory of descent, all the species in a genus are 

 descended from a common ancestry, but from a common ancestry 

 more remote than that common to the individuals constituting a 

 species. In grouping species in one genus all the characters of 

 the plants have to be taken into consideration, and we shall com- 

 monly find that all the species of any one genus will agree in the 

 number and insertion of their floral leaves, the kind of fruit, and 

 the general type of leaf; but that the species will differ from one 

 another in the size and form of the various parts. The mere 

 colour of petals or of fruit is generally considered only as a 

 varietal character. So far as a classification does take all the 

 characters of plants into account, it is a natural system ; whilst 

 one based only upon a single set of characters is an artificial 

 system. 



The best of all artificial systems is that of Linnaeus, based 

 primarily upon the number and arrangement of the stamens, and 

 secondarily upon the carpels. Like all other artificial systems, 

 this is a mere index, telling nothing about a plant beyond the 

 one character considered, separating plants obviously allied, and 

 placing together others which have but one character in common. 

 Linnaeus himself recognised the tentative character of his system. 

 " All plants," he says, in his " Philosophia Botanica," " are allied 

 by affinities, just as territories come in contact with each other on 



