48 Mutations and Evolution. 



The cruciate character. 



Coming now to the cruciata type of mutation, 1 (E. biennis var. 

 leptomeres of the Holland sand dunes differs from the species in 

 having narrow, linear petals, somewhat crumpled and more or less 

 greenish yellow. This constant form Stomps (1913) regards as a 

 case of incomplete sepalody, in which the petals have become 

 imperfectly transformed into sepals. In Epilobium he describes a 

 somewhat different form, E. hirsutum cruciatum de V., which 

 originated from a group of a dozen plants (perhaps derived by 

 stolons from one) and breeds true. The plants were found by Mr. 

 John Rasor in Woolpit, Bury St. Edmunds, and seeds were sent 

 to de Vries. They differ from the type in having, in place of the 

 large, obcordate, lilac petals, small greenish scales shorter than the 

 sepals, and pointed. That this is not a case of arrested development 

 is shown by examining the young buds of the species. The petals 

 are broad and obcordate even while still small and colourless. The 

 buds of the cruciate form show also a tendency to dry up and fall 

 when young. This appears to be a more complete case of sepalody. 

 Crosses between type and variety gave a Mendelian ratio. Thus 

 E. hirsutum cruciatum x E. hirsutum gave an F 2 of 323 plants, of 

 which 245 were type and 78 variety. Also the reciprocal cross 

 produced 177 plants in F 2 , 130 of which were type and 46 variety, 

 while one failed to flower. The sum of the two ratios is 375 : 124, 

 showing that the cruciata mutation is a simple Mendelian recessive 

 character. 



Not only does the cruciate mutation from (E. biennis differ 

 from that of E. hirsutum externally, but also in its hereditary 

 behaviour. For in reciprocal crosses of (E. biennis cruciata with the 

 parent type, while the F, is normal and the F 2 splits into the two 

 original forms, yet the ratios are not Mendelian. Stomps 

 unfortunately gives no figures, but states that whichever form is 

 used as the male parent, that form appears in the greater number 

 of the F 2 progeny. The cruciate forms in these two genera, 

 while comparable in general, are not therefore strictly parallel 

 forms. 



Elsewhere (1913a, p. 25) the writer has shown that, whatever 

 the origin of (E. lamarckiana var. cruciata, both normal and 

 cruciate flowers may occur on the same plant. This somatic 



1 See also Mutation Factor, p. 21. In addition to the specimen collected by 

 Ernst de Vries, others have been found on the Luneburg Heath, and they 

 have been reported from other parts of Holland, probably from independent 

 mutations. 



