78 STUDIES IX INDIAN TOBACCOS. 



Culture 163 probably represents the combination of all the factors 

 in Type 16 and Type 35. The total variation is no greater than 

 in Type 51. The average value in this culture is greater than 

 the combined average values of Type 16 x Type 35, but this may 

 be due to the added vigour due to hybridization. Further 

 cultures will, it is hoped, put the matter beyond question, and 

 any explanation must be tentative until these have been 

 examined. Culture 190 is probably uniform with regard to 

 this character. 



The cross Type 23 x Type 38 (Table XVI) is similar to that 

 between Type 9 and T^'^pe 51, except that neither parent has 

 non-decurrent leaves. The Fj is intermediate and the range of 

 variation in the Fo generation is the same as that covered by both 

 parents. It Avould seem therefore as if the same combination 

 of factors was common to both parents with the addition of extra 

 factors in one parent. Culture 155 is uniform and like Type 23, 

 culture 104 is possibly uniform and like Type 38, but this cannot 

 be assumed safely until further cultures are raised, as the 

 variability is somewhat great. The parent Type 38 and the 

 Fi generation exhibit very great variation in the same plant. 



6. VENATION OF THE LEAVES. 



The characters of the lamina itself will now be considered 

 and of these the venation has proved to be the most constant 

 and easily measured. A few words of explanation as regards 

 the choice of the material are necessary, and the following 

 explanation refers to all measurements on the leaves themselves. 

 The leaves of a tobacco plant are not all of the same kind, the 

 lower or ground leaves are very much alike in all the types and 

 are not characteristic of the variety. They are almost invariably 

 flat, and have a venation of 60°. This is the case even in Type 9, 

 in which the upper leaves are twisted by excess of undulation. 

 These ground leaves pass by a fairly rapid gradation into the 

 significant leaves, which are typical of the variety, and comprise 

 most of the leaves on the plant. The significant leaves increase 



