166 OENOTHERA LAMARCKIANA MUT. VELUTINA. 



belonging to one type, were discovered, but that no other deviation 

 could be observed. This gives a percentage figure of 0.1. If we com- 

 pare this with the table given on p. 337 of my Gruppenweise Art- 

 bildung, we see that 0. blandina falls into the group of those mutants 

 (0. nanella and 0. rubrinervis), the mutability of which has become 

 much smaller than that of the parent species, which latter is given 

 there as 2.2 per cent. The transition of one or more unit characters 

 into the inactive condition was considered there as the probable 

 cause of this change, and the same conception may obviously be 

 applied to our present case. 



Although the mutability of 0. blandina is thus seen to be very 

 small, it does not follow that it is wholly absent for other mutations 

 than the one mentioned. Casual mutations parallel to those of 0. 

 Lamarckiana may be expected to appear from time to time, either 

 in the pure strains or after hybridizations with other, still less 

 mutable, species. This has occurred once in my garden. Among the 

 offspring of a cross beteen 0. blandina and 0. Cockerelli, a species 

 from Colorado, an individual arose in 1915 which showed the marks 

 of 0. lata combined with those of 0. Cockerelli, and agreed with the 

 description given in my book (p. 254). It proves that the mutability 

 of 0. blandina into lata is not wholly absent. 



The mutation from 0. blandina, 4 specimens of which occurred 

 in my culture of 1915, was a strikingly new type, quite different 

 from all the mutations produced by 0. Lamarckiana and its deriva- 

 tives until now. It was distinguished at once by its linear leaves, 

 which could be seen in the boxes before the young plants were 

 planted out on the beds. The 4 mutants were brought into the glass- 

 covered part of my garden, where 2 of them have flowered. The 2 

 others remained small, produced stems, but died in the fall before 

 making any flower buds. Of the flowering specimens one was also 

 small and therefore was not used as a seed-bearer, but the other 

 reached about 1 m. in height, was very richly branched, and bore, 

 from July to October, many hundreds of flowers and fruits. All 

 these flowers had the same type, consisting of narrow petals instead 

 of the large cordate ones of the parental form. The petals did not 

 belong to the type called cruciata, inasmuch as they had not the 

 least sign of the sepalody characteristic of 0. cruciata and its allies. 

 Their color was uniformly yellow, not differing from that of 0. 

 Lamarckiana. The breadth varied from 0.5 to 1.5 cm. for a length 

 of 3 cm. The form was ovate, with some small indentations along 

 the margin, and the tip was narrowed and more or less spirally 



