GABRIELLE L. C. HOWARD, 



87 



Venation and ratio 



Table XXI. 



length 



breadth 



in F,^ Type i6 x Type 35. 



Ratio 



length 

 breadth 



40= 



45° 50° 



Size of Angle. 

 55° G0° 65° 70° 75° 80° 85° 90' 



No. of 

 Plants. 



Total 



1 13 54 48 97 65 69 38 43 14 



447 



Table XX. It will be seen that there is no true correlation 

 between these two characters, and this is confirmed by many 

 of the F3 cultures in which the venation was constant, but the 

 shape of the leaf very variable — culture 202 and many 

 others. There does, however, seem to be a limit to the occur- 

 rence of the higher angles. Those above 75° are only met with in 

 leaves with small ratios. A more detailed examination of the 

 venation affords a possible explanation of this, for that there is no 

 incompatibility between a large angle and a small ratio, is shown 

 by the banana leaf. There is a striking difference in the leaves of 

 the tobacco between the behaviour of the lateral veins which arise 

 at an acute angle and those in which the angle is large. The 



