5 



THE WHEAT PLANT 



The width of the blades of different leaves increases more or less 

 regularly from the lowest to the uppermost leaf of the culm : the average 

 breadth across the middle of the blades of the successive leaves of fifty 

 well-developed straws of T. vulgare (Squarehead form) was : 



Leaf. 

 Width 



ist 

 6-3 



2nd 

 9-2 



3rd 

 10-3 



4th 



5th 

 H'3 



6th 



17-1 mm. 



The longest leaves are possessed by T. turgidum and T. durum. 



In the following table is given the average separate lengths of sheath 

 and blade respectively, deduced from measurements of successive leaves 

 of the chief straw of fifteen plants of the different wheats mentioned. 



LENGTHS OF SHEATH AND BLADE (inches) 



DIFFERENCE BETWEEN SHEATH AND BLADE 



On comparing the figures it is seen that the length of the sheath of 

 successive leaves increases upwards, the uppermost being the longest. 

 The blades also exhibit a successive increase from leaf to leaf up to the 

 fifth, but that of the sixth or uppermost is always shorter than the blade 

 of the leaf below it. 



In all leaves except the terminal one the average length of the blade 

 is from 2| to 4 inches longer than the sheath associated with it ; but the 



