6 FRIEDA COBB 



the ratio of flat-leaved to revolute-leaved plants is 3.08:1, in very close 

 agreement with the expected 3 : 1 of the Mendelian monohybrid segregation. 



All progenies of fewer than 20 plants were omitted from table 2 as being 

 unreliable. A very small culture of flat-leaved plants might, had it been 

 larger, have included some revolute-leaved plants, and thus a heterozygous 

 dominant of the F 2 generation might be recorded as homozygous. If these 

 cultures were included in the table, the ratio of non-segregating to segre- 

 gating progenies would become 33:56 instead of 22:41, and the ratio of 

 flat-leaved to revolute-leaved plants in the segregating progenies would 

 become 2.94: 1 instead of 3.08: 1. 



Self-pollination of 16 plants of f . typica M (a'&FF) belonging to the non- 

 segregating cultures of the F 3 generation gave in the F 4 generation (see 

 table 3) 1114 plants, all of them flat-leaved. From these plants an F 5 

 generation has been grown, consisting of 695 plants belonging to 7 prog- 

 enies, no progeny consisting of fewer than 29 plants. All were flat-leaved. 

 Self-pollination of 3 plants chosen at random among the f . typica plants of 

 the segregating cultures of the F 3 generation gave in the F 4 generation (see 

 table 4) 2 segregating progenies and 1 non-segregating, showing a continu- 

 ance of the Mendelian splitting to the fourth filial generation. It seems 

 unnecessary to carry the line further. 



The behavior of the recessives, mut.formosa (a'Pff), of the F 2 generation 

 of the cross mut.formosa X mut. latifolia C. was also in accord with expec- 

 tation. The F 3 generation consisted of 69 plants belonging to progenies 

 of 4 mut. formosa plants of the F 2 generation. All were revolute-leaved, 

 and the 62 grown to maturity all proved to be mut. formosa. Also, 2388 

 plants belonging to the F 3 progenies from mut. formosa plants of the F 2 

 generation, of the. cross mut.formosa X CD hyb. viscida were all revolute- 

 leaved. Hyb. viscida is the form resulting from the cross Oenothera pratin- 

 cola f. typica C X Oenothera numismatica (BARTLETT 1915 a). It is like 

 f. typica C in all respects, except that, in addition to the pubescence nor- 

 mally occurring on the flowers of Oenothera pratincola, it has the viscid 

 pubescence of Oenothera numismatica. 



THE FI AND F 2 GENERATIONS OF THE CROSS F. TYPICA, STRAIN C X MUT. 



FORMOSA, STRAIN E 



j 



The Mendelian behavior following the cross mut. formosa X strain C 

 has been demonstrated at length. The reciprocal cross, f. typica C X 

 mut. formosa (afiFF X a'pff), is just as Mendelian in its segregation of the 

 free factors for flatness, but the Mendelian segregation of factors finds no 



