14 



DE. E. K. GATES— CONTEIBUTION TO A 



Oenothera Eooheri differs from 0. Lamarckiana and its mutants in its canescent 

 pubescence and the absence of crinkling in the leaves. 



O. omata apparently forms a transition to the smaller-flowered O. biennis forms, 

 though its style exceeds the stamens. It appears to differ from the latter in its 

 denser hirsute-pubescence and somewhat larger flowers with longer style. 



O. Tracyi in general characters agrees closely with O. grandijlora, from which it 

 differs chiefly in its smaller flowers with short style. 



O. biennis as now understood has leaves long, elliptic-oblanceolate to elliptic- 

 lanceolate, shallowly toothed and frequently with jagged teeth near the base. The 

 petals vary from 12-25 mm. long. 



O. Oalccsiana differs from 0. biennis in foliage, but also in having spreading sepal 



tips and large seeds. 



0. cayiovirens, another sefcresrate from O. biennis, differs from that form markedly 



\ 



tD^^'O 



in foliage, the petioles being somewhat succulent, the leaves much shorter, densely 



m 



cinereous-pubescent, and blue-green. 



O. 7^1iombipetala differs from O. biennis in foliage, but chiefly in having rhombic-ovate 



petals. 



0. strigosa differs from 0. biennis chiefly in being strigose, the foliage variable. 



O. chej^adophila differs from O. strigosa^ which it most resembles, chiefly in having 

 much smaller floAvers (petals 8 mm. or less) with shorter sepal tips. 



O. muricata differs constantly from the 0. biennis series of forms in having smaller 

 flowers (petals 9-15 mm. long). Most of the races also have narrow leaves, but 

 certain ones have broad leaves. 



O. parvijlora has still smaller flowers than O. muricata (petals 8 mm. long). It also 

 differs in foliage characters. 



O. Herlhaudi agrees with O. parvijlora in flower-size. It has the habit of O. biennis, 

 but has a long cxserted style, and its foliage resembles that of O. simiata, a form 

 which does not come strictly within the Onagra group. 



It is a matter of opinion how far O. OaJcesiana, O. canovirens, O. rJiombipetala, 

 O. strlgosff, 0. clieradophila and similar segregates from O. biennis should be recognized 

 as distinct species. " Splitters " will recognize many at least as such, while others, such 

 as Lev6ille in his monograph of the genus, will *' lamp " them all as races of one species. 

 That these different races will breed true there can be no doubt. Indeed, even smaller 

 differences remain constant in cultures. 



III. Eelationships of Species. 



General Distribution. — The genus OenotJiera is well-known to be exclusively American 

 in origin, although in the last three centuries, since its introduction into European 

 Botanical Gardens, it has escaped and is now naturalized and growing wild in many 

 parts of the world. In England, large-flowered forms related to O. LamarcMana are 



known to have been growing in great numbers on the Lancashire coast since at 

 least 1806 and probably much earlier. (Smith, in Sowerby, English Botanv, vol. xxii. 



