SPECIES AND GENEKA. 161 



far smaller than is usually supposed, and that many races, and a large 

 number of frequently recurring varieties, hold a place in our existing lists 

 of species. The varieties and races above mentioned are considered under 

 the development hypothesis as the initial stages in the formation of new 

 species. If these variations are of such a nature as to enable the plant ta 

 adapt itself better to the conditions under which it lives, or to sustain itself 

 in the battle of life with other organisms, then they will be perpetuated 

 become more constant, and ultimately attain such a degree of relative 

 constancy or invariability as to be classed as species. 



Genera. Whenever we examine a large assemblage of distinct 

 species, we shall find that certain of these agree with certain others 

 more closely than with the rest ; so that we may parcel them out 

 into groups, in each of which we shall find an agreement in a 

 number of common characters, by which it is also distinguishable 

 from the other groups. Generally speaking, we shall find that we 

 can place together a number of species agreeing closely in the 

 essential plan of construction of their floral organs, while they 

 differ in the forms and duration of their vegetative organs, &c. 

 Groups of this kind are called genera ; and the notion of a genus, 

 like that of a species, is not only common to all departments of 

 human knowledge, but is also existent in the language of common 

 life in its special natural-history sense, only requiring for scientific 

 purposes to be more strictly defined. In every language we find 

 generic names applied to plants, such as Willow, Rose, Violet, and 

 a hundred others, each of which terms is indicative of a group of 

 kinds or species, more or less extensive in different cases, corre- 

 sponding exactly in its logical value to the genus of the botanist. 



Some of these groups are characterized by very striking peculiarities, 

 so that even the genera of vulgar language correspond very nearly with 

 those of the botanist j but in the generality of cases the popular collective 

 names are applied on superficial grounds of resemblance, and include 

 widely diverse species. For example, the term Violet is made to bind 

 together not merely the common scented and other true Violets, but the 

 Dame's Violet (Hesperis\ a plant of the Cabbage family, the Calathian 

 Violet (Gentiana Pneumonanthe), a true and characteristic Gentian, the 

 Dog's-tooth Violet (Erythronium Dens-Cams), a plant of the Lily family, 

 &c. ; while the term Rose is extended from true Koses to Cisti, or Rock- 

 roses, Rhododendrons, Alpine Roses, &c. It is obvious here that there can be 

 no near " blood relationship," if we may so term it, between these so-called 

 Roses, &c. The classification of all these forms having only superficial 

 resemblance to each other is a purely artificial classification. Still some 

 genera are characterized in a sufficiently marked way for most of their 

 constituent species to be recognized as such pretty readily, after a very 

 small amount of attentive examination, as, for example, true Roses, 

 Willows, Lilies, &c. ; and we call such genera, including species of a 

 very marked similarity, " natural genera," thus indicating the closeness 

 of the band that ties them together. On the other hand, the principle of 

 combination which accords with the intuitive classification in those 



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