UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



BOTANY ''^' 



Vol. 5, No. 10, pp. 293-299 November 7, 1916 



ON THE PARTIAL STERILITY OF NICOTIAXA 



HYBRIDS MADE WITH N. SYLVESTRIS 



AS A PARENT. Ill 



AN ACCOUNT OF THE MODE OF FLORAL ABSCISSION IN 



THE F, SPECIES HYBRIDS 



BY 



T. H. GOODSPEED and J. N. KENDALL 



As pointed out in a number of previous papers, the Fj hybrids 

 between iV^. sylvestris and N. Tahacum varieties are in practice com- 

 pletely self-sterile. A small proportion of the ovules borne by these 

 hybrids are normally matured and capable of fertilization and the 

 production of viable seeds, and while it is probable that a correspond- 

 ing proportion of pollen grains are similarly capable of functioning 

 normally their relative number is so small that attempts to secure self- 

 pollinated seed have, up to the present time, been unsuccessful. As 

 a result of this non-success of self-pollination all flowers under bag 

 are abscissed at various periods following anthesis, and in the case of 

 unprotected flowers cross-pollination resulting in the maturing of a 

 very small quantity of viable seed is followed by the retention of less 

 than 1 per cent of the fruits commonly held upon a plant of one of the 

 parental species. In a previous communication a description has been 

 given of efforts, in general unsuccessful, to inhibit this characteristic 

 abscission of fruits, in which none of or only a very few of the ovules 

 have been successfully fertilized, and to increase the amount of nor- 

 mally matured sexual elements (cf. Goodspeed and Ayres, 1916). The 

 present paper aims to present the results of a considerable series of 

 preliminary experiments wliich have indicated the mode of abscission 



