100 STUDIES IN INDIAN TOBACCOS. 



A similar explanation to the series of independent indenta- 

 tion factors appears to hold good in the case of the leaf apex. 

 A curious feature of the leaves in some of the Indian tobaccos is a 

 sudden constriction of the lamina near the apex of the leaf, which 

 gives the appearance of a prolongation of the surface into a 

 long slender tip ; in others the tip is short. Good examples of both 

 these cases are seen in the Fo generation of Type 16 x Type 35. 

 (Plate XIX). At first sight it would appear as if this sudden con- 

 striction were absent in both parents but indications of it can be 

 detected in the apex of Type 16, although the narrowness of the leaf 

 has diminished its effect. Evidence as to the independence as 

 regards inheritance of the factors concerned in the configuration 

 of the apex is given in this Plate. Other examples are shown 

 on Plate XXIII. In 738-81, Nos. 14 and 60, are showTi two leaves 

 with similar apices but dissimilar widths, in 738-15, Nos. 38 

 and 96, are shoAvn two leaves with the same width, but dissimilar 

 apices, while 738-19, Nos. 68, 47 and 23, show the two extreme 

 forms of apex found in that culture with an intermediate form. 

 All these drawings are to scale. 



In three F3 cultures of the cross Type 16 x Type 35, the 

 leaves could be divided by eye as regards the configuration of the 

 apex, into three different groups giving a ratio 1:2: 1. This 

 shows that the plant was heterozygotic as regards one 

 apical factor only. Culture No. 9 gave 29 leaves with 

 broad apices ; 50 intermediate ; 30 with pointed apices. 

 Culture No. 35 gave 30 : 50 : 24. Culture 163 bred true as 

 regards the apex. These three cultures are illustrated in 

 Plate XXIV. 



No information is as yet available as regards the inheritance 

 of the presence and shape of auricles at the base of the leaf. 



It is hoped to publish a further paper on the factors con- 

 cerned in the leaf shape when the study of the pressed leaves 

 has been completed, but enough evidence has been given in this 

 section to show that the form of the leaf can be expressed by a 

 knowledge of the ratio length/ breadth, the position of greatest 



