316 TJniversity of California Puhlicafio)is in Botany [Vol. 5 



elements as furnishing a stimulus for a general increase in size in 

 the hybrid, but the sylvestris characters are not to be considered as 

 making up any considerable i^roportion of this increase. This state- 

 ment is not, however, to be construed as necessitating a denial of any 

 character influence of sylvestris in the hybrid, but merely as empha- 

 sizing the general fact that such influence is very slight indeed. 



In addition to a study of the Tahacum-sylvestris hybrid, Brown 

 has made a similar study of the hybrid of Tahacum and N. alata. 

 This hybrid has been figured by East and Hayes (1912, plate VIII) 

 and has also been reported upon by Naudin (1863). East and Hayes, 

 and Brown obtained hybrids which were much weaker than either 

 parent, but Naudin found the hybrid vigorous but tardy in develop- 

 ment. The difference may possibly be connected with the fact that 

 Naudin used N. macrophyUa as the Tahacum parent, whereas East 

 and Hayes, and Brown used much more vigorous and robust varieties 

 of Tahacum. The results, however, apparently agree in demonstrating 

 a striking resemblance between this hybrid and the alata parent. 

 Brown finds that in this case the alata influence is of about the same 

 extent as that of Tahacum in the hybrids of Tahacum and sylvestris. 

 Here the same criticism must apply as that given of the study of the 

 hybrids of Tahacum and sylvestris. Apparently in this case the alata 

 reaction system dominates the somatogenic processes, and the Tahacum 

 instead of stimulating development definitely inhibits it. An interest- 

 ing indication of the fact that Tahacum does, however, have some 

 influence beyond that of inhibiting the somatogenic processes is fur- 

 nished by the fact that the flowers are a very light pink, rather than 

 wliito as in alata, indicating that although the Tahacum elements are 

 for the most part incompatible with those of the alata system, never- 

 theless some of them are able to react slightly with this system and 

 to give characters which show a slight Tahacum influence. 



For other cases of species hybridization in Nicotiana (in addition 

 to the more recent work) we must consider the investigations of the 

 older hybridists, Kolreuter, Naudin, and Gartner, all of whom have 

 conducted extensive investigations of the phenomena following such 

 hybridization. Ever since Kolreuter (1761) employed the genus 

 Nicotiana in the classic experiment in which he crossed rustica and 

 paniculata, it has been a favorite subject for investigations in the 

 phenomena following hybridization. In spite of the extended period 

 over which the genus has been under investigation there are still many 

 uncorrected conti'adictions in the literature which deal with it. Focke 



