Varietäten, Descendenz, Hybriden. 319 



hybrides atteignent presque celle des grains paternels tres ecrases; 

 mais en longueur et en epaisseur ils surpassent les limites, pre- 

 sentes par les parents (Hybridmutation, Tschermak). Ils presentent 

 d'ailleurs la teinte rouge des caryopses maternels et sont beaucoup 

 plus epais que ces derniers. La deformation de l'ovaire est si evi- 

 dente qu'elle apparait meme nettement sur la Photographie et on 

 est tente d'y voir une justification de l'hj^pothese d'apres laquelle 

 rembr3''on hybride serait capable comme le parasite d'une galle de 

 deformer les tissus maternels d'une maniere specifique. 



Jongmans. 



Goodspeed, T. H., Quantitative studies ofinheritance on 

 iV/co//a;m-h vbrids. (Univ. Calif. Pub!. Bot. V. 2. p. 87—168. PI. 

 29—34. 1912.) 



I. The relation between the weights of hybrid Tobacco seed and 

 the inheritance of certain characters in Fo. 

 Summary of results: 



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

 cum var. macrophylla % y^ N. tabacuni 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 fiowers and the more gradually 

 tapering points of the leaves; all characteristic of virginica. 



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

 of the cross N. Tabacimi var. macrophylla $ X ^- tabaciim var. 

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



4. The divisions according to size, densit}^ and weight cor- 

 responded closel}^ — i.e., large seeds showed highest specific den- 

 sity and were the heaviest, eU:. 



5. Of the Jight 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 

 month's germination gave 88 per cent as the average of 1000 Jieavy 

 seed germinated, while the light and medium divisions of seed in 

 the propagating house gave such a low percentage of germination 

 that the total per cent of germination of 1000 li^ght and medium 

 seeds for the two months was ox\\y 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 maturit3^ 

 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. 



9. From the heavy seed 39 per cent of „dominants" (resembling 

 macrophylla), 9 per cent of „recessives" (resembling virginica) and 

 52 per cent of „intermediates" and „blends" could be distinguished. 



10. From the medium-weight seed 26 per cent of „dominants", 

 25 per cent of „recessives" and 49 per cent of „blends" and „inter- 

 mediates" can be reported. 



