Elementary Species in Nature 43 



proved to be constant in his pedigree-cultures. 

 Some of them have produced other forms, re- 

 lated to them in the way of varieties. They all 

 have nearly the same general habit and do not 

 exhibit any marked differences in their growth, 

 in the structure and branching of the stems, or 

 in the character of their foliage. Differentiat- 

 ing points are to be found mainly in the colors 

 and patterns of the flowers. The veins, which 

 radiate from the centre of the corolla are 

 branched in some and undivided in others; in 

 one elementary species they are wholly lack- 

 ing. The purple color may be absent, leav- 

 ing the flowers of a pale or a deep yellow. Or 

 the purple may be reddish or bluish. Of 

 the petals all five may have the purple hue 

 on their tips, or this attribute may be limited to 

 the two upper ones. Contrasting with this wide 

 variability is the stability of the yellow spot in 

 the centre, which is always present, and becomes 

 inconspicuous only, when the whole petals 

 are of the same hue. It is a general conception 

 that colors and color markings are liable to 

 great variability and do not constitute reliable 

 standards. But the cultures of Wittrock have 

 proved the contrary, at least in the case of the 

 violets. No pattern, however quaint, appears 

 changeable, if one elementary species only is 

 considered. Hundreds of plants from seeds 



