ORIGIN OF VARIETIES. ~ 92 1 



The characters which arise in single descendants are often only individual, 

 t. e. they are not again transmitted to their descendants. Thus the seeds of the un- 

 armed Robinia produce again spiny plants resembling, not their immediate ancestor, 

 but more remote ones ; while in other cases the new character is hereditary, though 

 at first perhaps only partially so, the new form making its appearance only in a 

 certain proportion of the descendants, while the others revert to the original form, as 

 in Duchesne's unifoliolate Strawberry. 



When a new character is transmitted by inheritance to new generations, the 

 number of individuals that revert to the primitive form often decreases from gener- 

 ation to generation, or the hereditary permanence of the new character increases ; 

 they become more and more constant, and sometimes even as much so as those of 

 the primitive form. Such new constant forms are termed Varieties^, 



The same parent-form may produce a smaller or larger number either simul- 

 taneously or in succession, sometimes even hundreds, of new forms ; and this is 

 especially the case with cultivated plants. The enormous number of varieties of the 

 Dahlia, differing in the colour, size, and form of the flowers and in their mode of 

 growth, now cultivated in our gardens, have been derived since 1802 from the simple 

 yellow-blossomed primitive form of Dahlia variabilis. The great variety of Pansies, 

 distinguished chiefly by the colour of their flowers, have resulted since 1687 from the 

 cultivation of the Viola tricolor of our fields with small flowers almost uniform in 

 colour^. Still more numerous are the varieties of Cucurbiia Pepo, differing not only 

 in the form of their fruit but also in all other characters ; and the same is the case 

 with the Cabbage {Brassica oleracea) and a vast number of other cultivated plants. 



Some plants have a special tendency to variation ; among native species, for 

 example, the fruticose Rubi, and those of Rosa and Hieracium ; others, on the con- 

 trary, are distinguished by great constancy in their characters, as for example Rye, 

 which has as yet produced no hereditary varieties, notwithstanding long cultivation ; 

 while the nearly related species of Wheat (especially Triticum vulgare, amyleum and 

 Speltd) are distinguished by a number of old varieties and an ever-increasing number 

 of new ones. 



By far the greater number of hereditary varieties are the product of sexual repro- 

 duction ; thus among Phanerogams the new characters appear suddenly in individual 

 seedlings which differ at once from the parent-plant in these respects. Sometimes 

 however it happens that particular buds develope differently from the other shoots 

 of the same stock ; and of this Bud-variation^ two different cases must be carefully 

 distinguished, since their significance is altogether different. In the one case the ab- 

 normal shoot of a stock which itself belongs to a variety resembles or reverts to 

 the primitive form ; and this therefore is an instance not of the production but of 

 the cessation of a new form. In the Botanic Garden at Munich there is, for example, 

 a Beech-tree with divided leaves, itself a variety, a single branch of which bears the 



^ For examples, see Hofmeister, Allgemeine Morphologie, p. 565. 



2 Darwin, The Variation of Animals and Plants under Domestication, vol. I. p. 368 et seq. 



3 [T. Meehan adduces a number of remarkable instances of bud-variation in which hybrid- 

 isation could not have taken any part;— in Rtibtts which rarely produces seeds in the wild state, 

 Cofivolviihis Batatas, which seldom flowers in America, &c. See Proceedings of the Philadelphia 

 Acad, of Nat. Sci. Nov. 29, 1870.] 



