1912] Goodspeed: Nicotiana Hybrids 145 



fairly closely the average corolla diameter of this "intermediate" 

 variety. 



6. Among' the corolla diameters of the flowers of all the 

 hybrid plants a wide range of fluctuation was observed. This 

 fluctuation included diameters from 13 mm. to 30 mm. 



7. The fluctuation 13 mm. to 30 mm. is as great as the differ- 

 ence between the smallest corolla diameter of variety III (the 

 small-flowered parental variety) — i.e., 13 mm. — and the largest 

 corolla diameter of variety I (the large-flowered parental variety) 

 — i.e., 29 mm. 



8. The maximum fluctuation in corolla diameter of a single 

 hybrid group of plants was 11 mm., or almost three times as 

 great as the parental type which fluctuated most widely — i.e., 

 4 mm. 



9. The minimum fluctuation for a single group of hybrid 

 plants was 7 mm., or almost twice as great as the largest fluctua- 

 tion in corolla diameters of the flowers of the three parental 

 varieties. 



DISCUSSION OF RESULTS 



One important exception must be noted to the statement 

 made in the introductory paragraphs of this paper, to the effect 

 that no critical attention has been given to F^ generation hybrids. 

 Reference is made to Darbishire's work on the nature of the 

 starch grains of round and wrinkled peas (Darbishire, 1908). 

 As will be remembered, the cross between a round pea with 

 potato-shaped or p starch grains and the wrinkled pea \^^th com- 

 pound or c starch grains yields a hybrid starch grain in F^ 

 which is intermediate in shape (length-breadth index), inter- 

 mediate in the distribution of compoundness. intermediate in 

 the degree of compoundness and the hybrid round pea itself is 

 intermediate in absorbtive capacity between the parents. In 

 F- "the homozygote round peas contain p-grains, the hetero- 

 zygote round peas contain r-ov intermediate, grains." Since this 

 work of l)arl)ishire's is practically the only experimental evi- 

 dence so far accumulated which is comparable with that wliieli 

 has been reported in the present investigation, it is necessary 



