1913] Goodspeed: Nicotiana Hybrids 197 



close other more fundamental difficulties in this connection that 

 have to do with the lack of a normal maturing of the sex elements 

 within the ovule, structural blocks to the proper penetration of 

 the micropyle, etc. In any case, however, it seems at least con- 

 ceivable — and the F2 generation which it seems possible may be 

 produced combined with cytological evidence will, it is hoped, 

 help to settle this point — that such few viable seeds as are 

 formed on these hybrids are produced apogomously or partheno- 

 genetically (East, 1912, p. 131), on the basis of the fact that less 

 than 1/100 of the number of viable seeds normal for the parental 

 species are produced in those F^ hybrids that mature any seed 

 at all. Finally there must at least be borne in mind the sug- 

 gestion which has also elsewhere been made (Goodspeed, 1913 

 (1), p. 179) in this connection that sexual reproduction vs. 

 vegetative reproduction may be definitely inherited "physio- 

 logical unit-characters" that behave alternatively in inheritance. 

 As bearing on this later point it may be said that vegetative 

 propagation by cuttings is comparatively easy in the case 

 of all the hybrids discussed above just as it is in the case of 

 .Y. sylvestris and in both cases this fact seems to be correlated 

 with a biennial or perennial habit w^ell known in the case of N. 

 sylvestris but, to my knowledge, not previously noted to the 

 same extent, at least, for N. Tabacum-Yarieties, the hybrids made 

 between them or for hybrids between N. Tabacum-yarieties and 

 N. sylvestris. Thus, Nicotiana sylvestris under field conditions 

 will reproduce itself " vegetatively " for at least three years. 

 The 1910 N. sylvestris X N. Tabacum var. macrophylla purpurea 

 crosses first grown in 1911 have similarly come up from their 

 own roots this year (1912) and the 1911 crosses growing this 

 year are forming adventitious roots wherever the lower materials 

 are in contact with the soil. 



