504 UniversUij of California Puhlicatians in Bodnty L^oi-. 5 



virginica and tlie red flower color of cahjcina. The third had the tall 

 stature of virginica and red flower color, in association with the hose- 

 in-hose flower form of colycina. These tliree lines apparently bred 

 true for all their characters, 



5. DISCUSSION OF RESULTS OF THE CALYCINA-VIRGINICA SERIES 



No extended discussion of results is indicated in connection with 

 the calycina-virginica series of hybrids because particular attention 

 was given to so few characters. Just as in the case of angusUfoUa- 

 macrophylla, so in this series of hybrids the character differences 

 proved to tiepend upon complex genotypic differences. Apparently 

 the flower color contrast in these two varieties was the same as that in 

 the angustifolia-macropliylla series, and the same relations with respect 

 to dominance and segregation were found to hold for it. Without 

 doubt we are dealing here with the Rr ])air of allelomorphs as in the 

 previous instance. The demonstration of tlie simple factor relations 

 in the inheritance of th(> split hose-in-hose form of flower adds to our 

 series another pair of allelomorphs which we may call Cc (calycine). 

 In this case the dominance of normal over split hose-in-hose appears 

 to be nearly, if not quite, complete. The sporadic appearance of split 

 hose-in-hose flowers on otherwise normal plants does not even seem to 

 be clearly associated with the heterozygous genotype, Cc. The data 

 for height are not of sufficient accuracy or extent to warrant an at- 

 tempt at Mendelian formulation. It was again found possible vei-y 

 easily to shuffle and recombine the characters occurring in the parent 

 varieties and to esta])lish recombination derivatives in pure lines. 



V. ALBA-MACROPHYLLA SERIES 



1. PARENTS OF THE ALBA-MACROPHYLLA SERIES 



Alba, which is one of the parents of the alha-macropliylla series, 

 is the "White" tobacco, U. C. B. G. 30/06, described by Setchell. It 

 is one of the taller forms of Tahacuni, ranging in height from 165 to 

 220 em. Typically aJha is unbranched below; above, it has flowering 

 branches corymbosely arranged in succession from above downward. 

 The leaves are sessile, more, ample, more rugose, and more velvety than 

 those of macrophyUa. They are narrowed suddenly above the ex- 

 panded, somewhat aurieled and partially clasping base. The leaves 



