256 Holmes. — A Contribution to the Study of 
the lumen as 0*06 mm. In the present paper variation in the average 
diameter of the vessels for different shoots and different parts of the same shoot 
will be illustrated, but at this point it may be mentioned that the extreme 
range of individual diameter among the measurements made for these 
young plants is 67 to 3 ju. 
Method. 
In working out statistics for the size and proportion of the water- 
conducting elements in the wood, a method similar to that previously 
described for Hazel and Ash has been followed (6 and 7 ), the data being 
obtained from transverse sections of the wood taken at the middle points of 
the selected internodes. The figures are only approximate, of course, and 
contain no information as to the longitudinal characters of the elements, or 
the resistance at the nodes. In all cases graphs were drawn from these 
figures to be comparable with those constructed for Hazel and Ash; the 
same vertical scales were taken for all, while the horizontal scale for the 
Sycamore is the same as that for the Ash, and double that for the Hazel, to 
correspond with the number of leaves borne at each node. 
Here it is necessary to explain that a mistake appears in the results 
given in the Hazel and Ash papers, which the writer much regrets. The 
figures for B were worked out on the basis of a formula in which the squaring 
