108 University of California Publications in Botany [Vol. 5 



VIII. SUMMARY OF RESULTS 



1. The hybrid in F^ produced from the cross Nicotiana Tah- 

 acum var. macrophylla JX '^- Tahacum var. virginica ^ resembles 

 more closely the macrophylla parent. 



2. The absence of complete dominance of the macrophylla 

 parent was shown by the occurrence in the F^ heterozygote of the 

 ruffled auricle, the hooks terminating the shallow angles of the 

 pentagonal corolla limb, the lighter color of the flowers and the 

 more gradually tapering points of the leaves; all characteristic 

 of virginica. 



3. The seeds produced by close fertilizing one F^ hybrid plant 

 of the cross N. Tahacum var. raacrophylla^y, N. Tahacum var. 

 virginica ^ showed a great variation in size and in weight. 



4. The divisions according to size, density and weight cor- 

 responded closely — i.e., large seeds showed highest specific den- 

 sity and were the heaviest, etc. 



5. Of the light and medium seed 65 per cent germinated in 

 the germinating case within a month, while only 49 per cent of 

 the heavy seed germinated during the same period and under 

 the same conditions. 



6. During a month in an unheated propagating house the 

 heavy seed germinated to such an extent that the final count 

 for the two months' germination gave 88 per cent as the average 

 of 1000 heavy seed germinated, while the light and medium divi- 

 sions of seed in the propagating house gave such a low percent- 

 age of germination that the total per cent of germination of 

 1000 light and medium seeds for the two months was only 78 per 

 cent. 



7. The number of plants in the field four months later showed 

 that a larger percentage of the seedlings set out into the field 

 from the light and medium grades of seed had come to normal 

 maturity than from the heavy seed. 



8. The appearance of the F^ generation individuals made it 

 possible to distinguish four classes of plants, the division being 

 based upon the combinations of the distinguishing characters of 

 the two parents which they exhibited. 



