OENOTHERA LAMARCKIANA MUT. VELUTINA. 167 



twisted. This latter mark, which was best visible during the time 

 of the most abundant flowering, has induced me to choose for this 

 mutation the name of 0. spiralis. 



As to the other marks, they were probably all evolved under the 

 influence of the very narrow leaves, which could not produce food 

 enough for very stout individuals or organs. The leaves measured 

 5—6 mm. in breadth by a length of 8—10 cm.; they were smooth 

 (without bubbles) as in the parent, not folded longitudinally, only 

 a little hairy, and dark green. The internodes were long, reaching 



2 cm. or more, and the foliage was therefore thin and the whole 

 habit slender. The flower buds were less hairy than in 0. blandina, 

 but more so than in 0. Lamarckiana, and broader than would be 

 expected from the narrow petals. The stigma was above the anthers, 

 which contained a good supply of pollen, making artificial self- 

 pollination and crossing quite easy. The fruits were rather thin, 

 and somewhat smaller than those of 0. blandina, a little more conical, 

 and less hairy. 



It should be pointed out that the origination in 4 specimens, one 

 from one parent and the 3 others together from another parent, 

 is analogous to the production of 0. blandina itself, which arose in 



3 specimens from one lot of seeds. It points to an internal condi- 

 tion of heritable mutability and suggests the expectation that under 

 a better climate and with more suitable conditions of cultivation 

 the number of simultaneous mutations in the same direction might 

 increase sensibly. 



Crosses of 0. blandina with other species. — In order to give 

 proof that 0. blandina is really the mutant velutina, I made some 

 crosses with such species as are known to split 0. Lamarckiana 

 and some of its other derivatives into the twin hybrids laeta and 

 velutina. It is obvious that with the loss of the active qualities of 

 laeta this capacity of undergoing a splitting must disappear. The 

 mutant velutina corresponds to the latent or inactive condition 

 of these qualities, and if combined with splitting species it must 

 therefore give rise only to one of the twins, the hybrid velutina. 

 In other words, the crosses with these species must be expected to 

 produce no laeta but only velutina hybrids, and these must be exactly 

 the same as the velutina issued from the corresponding crosses of 

 0. Lamarckiana. 



Under normal conditions the splitting of this latter species occurs 

 in nearly equal groups of both the twins, but as a matter of fact 

 the external circumstances are, with us, often such as to diminish 



