264 MUTATIONS OF OENOTHERA SUAVEOLENS DESF. 



so far as they do not return to Oe. suaveolens, but their progeny is 

 very rich in mutants of the alternating narrow-leaved type and of 

 mut. lutescens. 



8. Crosses of Oe. suaveolens with allied species (Oe. biennis, Oe. 

 syrticola and Oe. biennis Chicago) give intermediate and constant 

 hybrids, which are often different for the reciprocal combinations. 

 Double reciprocal crosses between this species and Oe. biennis 

 resemble the peiipheral parent in the formula, with a more or less 

 complete exclusion of the central one. They run parallel in this 

 respect to the double reciprocals between Oe. biennis and Oe. syrticola. 



9. Crosses with Oe. Lamarckiana for which Oe. suaveolens yields 

 the pollen, give a unifoim and constant progeny of an intermediate 

 type, excepting the occurrence of mutants of the type of lutescens. 

 The same hybrids result from the cross with Oe. Lamarckiana na- 

 nella and Oe. Lamarckiana lata, but in the latter case 40—46 percent 

 specimens with the type of lata arose. In these cases the behavior 

 of Oe. suaveolens is the same as that of Oe. biennis. 



10. The fecundation of Oe. suaveolens by Oe. Lamarckiana yields 

 the twin hybrids lacta and velutina, besides mutants of the lutescens 

 type. The laeta and velutina each repeat their own type in the next 

 generation. 



11. From all these crosses we may infer that many prominent 

 hereditary qualities are the same or almost the same for Oe. sua- 

 veolens and Oe. biennis. But in respect to the production of mutants 

 they aie, as we have seen, largely different, the main difference 

 being the production of Oe. lutescens in percentage figures which 

 indicate a secondary or mass mutation. It seems probable that this 

 latter is connected with the presence of about one-half of empty 

 grains among the seeds. 



LITERATURE CITED 



Bartlett, H. H., 1915a Mutation en masse. Amer. Nat. 49 : 129-139. 



1915b Mass mutation in Oenothera pratincola. Bot. Gaz. 60 : 425—456. 

 Blaringhem, L., 1914 L'Oenothera Lamarckiana Ser. et Ies Oenotheres de la 



foret de Fontainebleau. Rev. gen. de bot. 25 : 35—50. 

 Gagnepain, F., 1900 Sur un hybride artificiel Oenothera suaveolens X biennis. 



Bull. Assoc. Franc, de bot. Aout-Septembre. 

 Gates, R. R., 1915 The mutation factor in evolution, pp. xiv -f- 353. London: 



Macmillan. 

 De Vries, 1913 Gruppenweise Artbildung. pp. viii -f 365. Berlin: Gebr. Born- 



trager. 

 1914 L'Oenothera grandiflora de l'herbier de Lamarck. Rev. gin. de bot. 



25: 151-167. Opera VI, p. 564. 



