8. Abstammungslehre. 53g 



toren des Bakteriums leistungsfähig und es kann somit zu einer völligen 

 Hemmung des Wachstums nicht kommen, in seiner Nahrungsaufnahme ist das 

 Bakterium aber geschädigt. Der Ausdruck dieser Schädigung ist die partielle 

 Wachstumshemmung. Seitz (Königsberg i. Pr.). 



1505) Vuilleilliii, P., Mutation d'un hybride transmise ä sa poste- 

 rite et ä ses produits en voie de disjonetion. 



(Compt. Rend. Acad. des Sc. de Paris 153,11. p. 551—553. 1911.) 

 Un petunia a präsente des lobes interpetalaires opposes aux etamines. 

 Cette mutation s'est reproduite abondamment dans la lignee issue de cette 

 plante, qui a presentö en meme temps des phenomenes de disjonetion. 



C. L. Gatin (Paris). 



1506) Gates, R. R., Mutation in Oenothera. 



(Amer. Naturalist 45. p. 577—606. 1911.) 



This paper is a summary of several lines of the writer's work in con- 

 nection with the study of the mutation phenomena in Oenothera. The fact in 

 first emphasized, that natural wild species of open-pollinated plants are not 

 „pure lines", but are hybrids, in the sense that many closely-related races 

 have contributed to their ancestry. The large-flowered Oenotheras, such as 

 0. Lamarckiana and 0. grandiflora, are therefore not pure races, either 

 in nature or in gardens. It is further pointed out that each of the „species", 

 0. Lamarckiana, 0. grandiflora, 0. biennis and 0. muricata, containe 

 a large number of races which will breed true. Many of these races have 

 been grown in eultures from wild seeds and seeds from numerous Gardens. 



After an extensive study of the early records and figures of Oenotheros 

 in European Gardens, the early history of the species above-mentioned is 

 fairly well determined. The earliest aecount of 0. grandiflora Ait. (which 

 may also have included 0. Lamarckiana Ser.) is in Ray, 1686, under the 

 nome Lysimachia Virginiana altera, foliis latioribus, floribus luteis 

 majoribus. Plukenet figures 0. muricata in 1696, and Barrelier in 1714 

 figures three species which are 1. 0. biennis, 2. 0. muricata, while 3. be- 

 longs in the 0. grandiflora-Lamarckiana series which have large flowers 

 and are open-pollinated. 



Examination of the type speeimens for Linnaeus' „Species Plantarum" 

 and „Hortus Cliffortianus" shows that certain of them belong to the „Euro- 

 pean biennis" (having larger flowers than the American races of 0. biennis), 

 while one race was open-pollinated and therefore come nearer 0. Lamarckiana. 

 Other early herbarium collections in London show that forms very closely 

 similar to if not identical with 0. Lamarckiana and 0. rubrinervis, for- 

 merly oecurred in the Western United States. 



It is pointed out that both 0. grandiflora and 0. biennis were for- 

 merly found wild in the region of Virginia, so that, if 0. Lamarckiana 

 originated from crosses of these races, its origin must have oecurred there 

 centuries ago in the wild condition. But since, in all open-pollinated forms, 

 continual crossing of races is taking place, it is neither necessary nor possible 

 to discover just what those crosses may have been. The evidence offered by 

 Davis to show that 0. Lamarckiana is derived from 0. grandiflora and 

 0. biennis is not sufficiently critical, the flowers of his hybrid being only 

 about half as large as in 0. Lamarckiana. 



Extensive eultures of Oenotheras which have long been naturalized on the 

 English sand dunes, have isolated a large group of new races whose flower- 

 characters closely resemble those of 0. Lamarckiana and 0. grandiflora. 



36* 



