50<) 



THE AMERICAN NATURALIST [Vol. XLVIII 



lighter yellow, and is reported by de Vries to be not uncommon 

 in the wild state mixed with the species proper. Sulfur* a has 

 been held systematically to he a variety of biennis but this is the 

 first time that it has appeared in the experimental garden as a 

 derivative of that species. Thus out of a total of 920 plants 

 there were 4 individuals of the color variety sulfurea, 1 nanella 

 and 1 semi-gigas, in all 6 mutants.' a showing that may well 

 grat it'y Stomps. 



The mutant biennis nandla differed from typical biennis in 

 much the same way that Lamarckiana nanella differs from 

 Lamarckiana and like the latter dwarf showed evidence of a 

 bacterial infection. Certain selfed flowers set no seed because 

 of diseased stigmas. Other flowers pollinated from pure biennis 

 set good fruit. The ratio of the appearance of biennis nanella 

 is much lower than the mutation coefficient of one per cent, which 

 de Vries has reported for Lamarckiana nandla. It should also 

 be remembered that de Vries 1 obtained a cruciata nanella in a 

 culture of 500 plants from 0. biennis cruciata. 



The mutant biennis semi-gigas in comparison with typical 

 biennis showed a stronger habit, broader leaves, thicker buds, 

 larger flowers, supernumerary stigma lobes, and the presence 

 of 4-cornered pollen grains. Counts of the chromosomes in 

 meristematic tissue determined the number to be 21. Therefore 

 in this plant, as in the biennis semi-gigas obtained by Stomps 

 from the cross cruciata >< biennis, there is clear cytological evi- 

 dence that one of the gametes which formed the zygote contained 

 14 chromosomes, i. c., double the number characteristic of the 

 gametes of (Enothcra. This is another case of triploid mutants 

 in (Enothera to be added to the list of Stomps and Miss Lutz. 

 The plant was self sterile, but set fruit when pollinated by 

 biennis, although the yield of seed was very poor. 



Stomps is justified in calling attention to the agreement of his 

 second biennis nanella with the plant derived in 1911 from the 

 cross biennis X cruciata, and of the agreement of his second 

 biennis semi-gigas with the plant from the cross cruciata X 

 biennis. It is to be hoped that he will next obtain the cruciata 

 variety as a direct mutant from the Dutch biennis and thus 

 establish its relationship and origin beyond all possible doubt. 



Stomps has before him the opportunity of making through the 

 study of GJnotJura biennis very important contributions to our 



< See "Gruppenweise Artbildung, " p. 299 and Fig. 108. 



