202 LOCK : 



an exactly intermediate position between the constituent species. 

 We, on the other hand, consider the type of N. paniculata to 

 exert a predominating influence both in N. rustico-paniculata and 

 in N. paniculato-rustica. 



Whilst, in the opinion of the present writer, N. rustico- 

 paniculata is on the whole distinctly nearer to N. rustica than 

 to N. paniculata. 



On p. 256 of the same work Gsertner gives the following 

 further examples of the " prepotency " of one species over 

 another in the genus Nicotiana : — 



The hybrid between N. suaveolens and N. vincaeflora is a 

 notable example of this phenomenon ; this when crossed with N. 

 langsdorfii preserves its own type so closely that the only points 

 in which a difference can be found are a separation in the stamens 

 from the tube of the corolla, the blue colour of the anthers, the 

 greenish colour of the corolla, and the curvatiire of the tube. In 

 the hybrid suaveolenti-macrophylla , on the other hand , suaveolens 

 is not recognizable, and macrophylla strongly predominates. One of 

 the most remarkable examples of the predominance of one type and 

 of transformation( Verwandlung) is shown by the hybrid paniculato- 

 vincffiflora, in which N. paniculata is so completely transformed 

 into the type of vincseflora that the hybrid only shows slight 

 differences in its smaller greenish flowers , the rounded , markedly 

 smaller, white limb, the partial separation of the stamens from 

 the straight tube, the rather wider leaves and the weaker branch- 

 ing ; whilst no marked difference is to be seen either in the general 

 growth and habit of the plant or in the general form of the leaves 

 with their wrinkled surface. On the other hand, in the hybrid 

 between this species and N. quadrivalvis (N. quadrivalvi-vincse- 

 flora) the influence of the seed parent is unmistakable. 



To a smaller degree the influence of the pollen parent is said 

 to predominate in N. rustico-quadrivalvis and in N. glutinoso- 

 quadrivalvis, and that of the seed parent in N. grandifloro- 

 glutinosa. None of the hybrids here mentioned by Gsertner 

 have come under my personal observation. 



4..— IMPOSSIBLE COM BIN A TIONS. 



Taking the flowering plants as a whole, Gaertner found, in 

 attempting various species crosses, every possible degree of 

 resistance to the normal effect of the act of fertilization. 



From pollen, which is said to have an actually toxic effect, 

 through pollen to which the female organs of the intended 



