C. A. BARBER 



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of this relative prominence, the width of the midrib was measured at the same 

 time and place as the width of the lamina in the above table. The midrib may 

 be studied from two standpoints, firstly, its own intrinsic width, and. secondly, 

 the relation this bears to that of the lamina. 



{a) Width of midrib in different parts of the leaf. 



We see from these figures that the midrib is distinctly wider in the leaves 

 of the Saretha series all the way up, and this is the more noticeable when 

 we remember that the leaves are wider in the Sunnabile group, especially 

 in this lower part of the leaf. 



(6) Relative width of lamina and midrib. To give expression to this 

 the width of lamina has been divided at each point by the width of midrib. 

 The following figures give the quotients : — 



And the table gives a useful expression of the comparative inconspicuous- 

 ness of the midribs in the Sunnabile series. 



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