Shull: Three New Mutations 



357 



LEAVES OF FUNIFOLIA AND ITS PARENT, IN CROSS SECTION 



The lower diagram represents a leaf of the fiaiifolia in cross section, the upper one, a leaf of 

 Oe. Lamarckiana. (Fig. 10.) 



Fig. 16. At this stage the characteris- 

 tic constrictions between the lateral 

 veins are not present. The revolute 

 leaves and grayish aspect suggested 

 at first that these five plants were dis- 

 eased, but it was demonstrated later 

 that they were permanent normal 

 hereditary characteristics. 



This sudden quintuple appearance of 

 a striking new type which had never 

 before appeared in the extensive cul- 

 tures of Oe. Lamarckiana, illustrates 

 the phenomenon which Bartlett has 

 called "mass-mutation," and the breed- 

 ing tests which have indicated the 

 method of origin of funifolia, may be 

 used as a basis of interpretation of other 

 cases of so-called "mass-mutation." 

 The crosses of these five funifolia 

 plants with their Lamarckiana sibs, 

 and with Lamarckiana plants in other 

 families, showed that the parent of 

 family 1720 had been heterozygous 

 for funifolia, but that the funifolia 

 factor did not occur in any of my 

 other Lamarckiana families, either in 

 the independent strains or in the fami- 

 lies most closely related genetically to 

 family No. 1720. The conclusion 

 seems justified therefore that the 

 funifolia factor arose as a gene-muta- 

 tion in 1916 in the production of the 

 egg or the sperm whose mating resulted 

 in the parent of family No. 1720. 



Since Oenothera Lamarckiana is main- 

 tained in a heterozygous state by the 

 presence of the two lethals, h and k, in 

 chromosome I, funifolia could become 

 visible only through the process of 

 crossing over. The relatively frequent 

 crossing over of the funifolia factor 

 from chromosome la into chromosome 

 \h or vice versa shows that there is an 

 appreciable distance (possibly about 20 

 units) between the locus of the fmiifolia 

 factor and the loci of the characteristic 

 Lamarckiana lethals, k and h- The 

 only difference between "mass-muta- 

 tions" and single (crossover) mutations 

 is attributable to the fact that the loci 

 of the former are relatively distant 

 from the limiting lethals while the loci 

 of the latter are very near to the 

 lethals. 



OTHER PARALLEL MUTATIONS 



Perhaps the most interesting fact 

 regarding mut. funifolia, is its status 

 as a probable parallel mutation, since 

 its characteristics are in essential agree- 

 ment with those of Bartlett's Oe. 

 pratincola mut. formosa. Oenothera 

 pratincola and Oe. Lamarckiana are so 

 unlike in every way that one can not 

 logically assume a common ancestor 

 except in a relatively remote past. If 

 it should turn out, as I anticipate, that 

 the funifolia factor in Lamarckiana 



