86 



STUDIES IN INDIAN TOBACCOS. 



the second, that all the measurements such as width, length 

 and venation are made on the same leaf. Comparative deter- 

 minations on the same cultures by both methods give similar 

 results. In most cases in 1913, the data given are the mean of 

 two determinations, but experience shows that where time is 

 limited one careful determination is quite sufficient. The 

 difference between the determinations was not greater than the 

 error of measurement. 



The angle of venation appears to be extraordinarily 

 constant for any one type (see Table XVII) and to be 

 largely independent of the shape and width of the leaf. 

 This is shown very well by Type 9, in which the angle remains 

 constant at 50°, while the shape and width of the leaves varies 

 greatly. An examination of Table XX shows that the angle of 

 venation in the Indian types varies from 35° to 90° and that all 

 the intermediate grades occur. The smallest angle, 35°, is found 

 on a comparatively broad leaf. In Table XXI the relation 

 between the venation and the shape of the leaf as expressed by 

 the ratio length/breadth of the leaf is shown for the Fg generation 

 of Type 16 and Type 35, and also for all the Indian types on 



Table XX. 



length 



Venation and ratio of the leaf in the various types of N. tabacum. 



breadth 



Venation. 



Length. 

 Breadth. 



Venation. 



Length. 



Breadth. 



Venation. 



Length. 



Breadth. 



Venation. 



Length. 

 Breadth 



35° Type 19 2.4 



40° 



45° 



10 

 11 

 12 

 13 

 14 

 20 

 21 



4.1 

 4.4 

 4.1 

 3.5 

 3.3 

 3.0 

 3.8 

 2.6 

 2.8 



22 2.3 



50° Type 



55° 



60° 



6 



9 



16 



18 



27 



17 

 26 

 30 

 31 

 36 

 4r, 



4.1 

 3.6 

 4.1 

 3.0 

 2.6 



25 2.8 



2.8 

 2.4 

 2.4 

 2.1 



2.0 



2.r, 



60-65° Type 38 1.7 



65° 



70° 



33 



1.9 



75° Type 



90° 



23 2.3 



37 2.7 



41 2.1 



39 2.0 



50 1.8 



