138 ATKINSON— TWIN HYBRIDS. 



plants in the Fo of this culture. The pycnocarpa type is not fixed 

 in the F^, but splits in the F. into two types, the pycnocarpa type 

 and the franciscana type. Of the 50 rosettes in the culture, 13 were 

 of the pycnocarpa type, and 37 of the franciscana type. The two 

 types which result from the splitting of the pycnocarpa type in the 

 F2 are shown in Fig. 7 (=157.33), PI. IV., pycnocarpa type; 

 and in Fig. 8 (= 157.10), PI. IV., franciscana type. 



Franciscana type Fo, No. 138 (pycno X fran). — There were 64 

 rosettes of this type in the Fo, all of the franciscana type. There 

 is no splitting of the franciscana type in the second generation, but 

 the fluctuating variations in the rosettes are quite marked. These 

 variations relate to the size and shape of the leaves, and parallel 

 the fluctuating variations of the leaves in the rosettes of the parent 

 Qinothera franciscana. 



Of the reciprocal cross {Oenothera franciscana X pycnocarpa) , 

 only the pycnocarpa type twin was grown in the F... There were 42 

 plants, most of them developed into mature, autumnal rosettes, but 

 in a few premature stem development checked rosette development. 

 Splitting in the second generation occurs here also. There were 39 

 rosettes of the franciscana type and 4 of the pycnocarpa type. 



Fluctuating Variations in the F^ Hybrid Types. — In the second 

 generation in all of the hybrid types of the crosses between CE. 

 franciscana and pycnocarpa the fluctuating variations as shown by 

 the rosettes were very marked. These variations were studied more 

 carefully in the franciscana types. It was possible to recognize 

 several groups into which the principal variations could be assembled, 

 although the limits of variation in the several groups were not clear 

 cut. The groupings are as follows : 



Series No. 157, Fo of pycnocarpa type (pycno Xfran). In the 

 splitting between the 50 plants in this culture there were 15 of the 

 'pycnocarpa type and 30 of the franciscana type. The groups of 

 variation in the franciscana type, with the number of rosettes in 

 each group, are as follows. 



1. Leaves medium broad, dark green, white-veined, 3. 



2. Leaves broad, dark green, crinkled, pink-veined, 17 (6 of them 



rather narrow leaved). 



3. Leaves narrow, dark green, white-veined, 4. 



