88 ELEMENTARY BOTANY. 



all thus characterized. The amount of variation, within 

 varietal limits, cannot of course be dogmatically determined ; 

 some botanists may, in particular cases, call species what 

 others designate as merely good varieties. In general, varie- 

 ties may be regarded as incipient species. 



3. An individual of any species may occasionally show a 

 conspicuous -variation from the typical form ; as a Violet without 

 a spur, a Strawberry plant with simple leaves, a regular flower 

 when the flowers of the plant are labiate, and so on. Such 

 characters are not transmitted to descendants : the latter pre- 

 sent the typical form. Individuals behaving in this manner 

 are called sports. Exaggerations of such tendencies produce 

 monstrosities. These are sometimes very instructive, espe- 

 cially in cases of reversion. Thus in a monstrous flower, the 

 several organs may revert to the form of leaves, of which evi- 

 dently, therefore, they must be considered modifications ; or 

 a flower-bud may develop into a branch, showing that the 

 flower is homologous with the latter. The influence of culti- 

 vation in producing monstrosities, sports, races, and " varie- 

 ties " (in the sense understood by gardeners) is very marked. 

 Thus, there are hosts of forms of the Dahlia in cultivation, 

 all derived since 1802 from Dahlia variabilis ; the Pansies, 

 from Viola tricolor, are also numerous ; " some Melons are no 

 larger than small plums, others weigh as much as 66 pounds ; 

 one variety has scarlet fruit, another is only one inch in diam- 

 eter, but three feet long ; one variety can scarcely be distin- 

 guished externally or internally from cucumbers ; one Alge- 

 rian variety suddenly splits up into sections when ripe." 

 (Darwin.) 



4. The several species of Willows have a marked resem- 

 blance to each other ; the same may be said of the various 

 Oaks, the Osiers, the Clovers, the Violets, etc. A group of such 

 nearly-related species is designated by the word genus. Thus, 

 there is a genus of Oaks (Quercus), a genus of Roses (Rosa), a 

 genus of Toad-stools (Agaricus), a genus of Rusts (Puccinia), 

 and so on. The genera including the Bean (Phaseoltis), Pea 

 (PisiMTi), Vetch (Vicia), a.nd many others have a general re- 



