1912] Goodspeed: Nicotiana Hybrids 147 



crossed (Darbishire, 1911, p. 211). The F^ hybrid was a blend, 

 corresponding, probably, to the intermediate position occupied 

 by the F^ hybrid starch grains above mentioned, and, "so far 

 as data at present available show, segregation does not occur 

 when the hj'brids are self-fertilized." The author raises the 

 question whether, in such experiments, the Fo generation might 

 not consist "of a complete series of gradations between a 'small' 

 identical with the pure 'small' at one end, and a 'large' identical 

 with a pure 'large' at the other end" (Darbishire. 1911, p. 211; 

 but see also Castle, 1905, and Bateson, 1909, p. 251). The possi- 

 bility at once suggests itself that just this same condition of 

 partial segregation is present in the F^ hybrids of the N. acum- 

 inata crosses — in other words that, just as large seeds, small 

 seeds and seeds showing all gradations in size between large and 

 small might occur in the ripe pods of the hybrid peas in Fj, so 

 on a single plant of the N. acuminata hybrids in F^ large flowers, 

 small flowers and all degrees of intermediate flower size occur. 

 As the author suggests, again, the only practical value of con- 

 tinuing to breed from material showing such a type of inherit- 

 ance is the possibility that one or both the extremes of the series 

 may breed true in later generations and that a certain propor- 

 tion of the intermediate forms, probably those nearer the ex- 

 tremes, may also breed true. With this in mind, it has been 

 possible to secure F, seed from hybrid flowers on one plant, the 

 corolla diameters of which were large, small, and intermediate 

 in size between large and small. Thus the suggestion that can 

 in general be made is that such segregation as will definitely 

 occur (Bateson, 1909, p. 211) in respect to the corolla diameters 

 of hybrid flowers of N. acuminata, is exhibited in the flowers of 

 the F^ generation hybrids and that the F2 generation will show 

 whether or not certain corolla diameters breed true or whether 

 the fluctuation in corolla diameters which appeared in the hybrid 

 flowers will be regularly diminished in Fo and succeeding genera- 

 tions until the two parental types are ultimately regained and 

 a number of new "flower-size" varieties, with small fluctuations 

 in corolla diameters, are established. 



Certain results obtained by Groth (1911, part 1, pp. 5-10) 

 in liis examination of the cotyledons on F^ hybrid tomato seed- 



