BROWN ON IDKNTIPYING SPl'X'IES OF WOOD. 109 



WOOD STRUCTURE OF ELMS, MAPLES AND OxVKS AS A MEANS 



OF IDENTIFYING SPECIES. 



R. L. BROWN. 



Wood of the broad leaved trees is composed of three elements techni- 

 cally known as wood fibers, wood parenchyma and pitted ducts. Mnch 

 the larger part is composed of slender wood fibers that run lengthwise 

 of the tree and give strength to the timber, the exceeding variability of 

 these fibers renders it practically impossible to find any characters con- 

 stant enough for use in identification. The thickness of the cell walls is 

 the most uniform characteristic. 



Extending crosswise of these fibers or radially in every direction from 

 the pith are the medullary rays or wood parenchyma. They begin just 

 outside the pith and are continuous to the bark where new ones are added 

 each year as the tree grows. 



The rays may be described as fine or large, conspicuous or indistinct. 

 The length is the dimension from the pith outwards, the breadth is at 

 right angles to the length and extends up and down the tree, the thick- 

 ness extends across the tree perpendicular to the plane of the length and 

 breadth. Most trees have small rays between the larger ones that never 

 attain the size of the larger. These will be spoken of as fine or inter- 

 mediate rays. 



The third element is the large pitted ducts that extend up and down the 

 tree as long tubes. They serve as a means of conveyance and are for the 

 purpose of identifying wood, the most important. 



To my knowledge comijaratively little work has been done upon wood 

 structure and for this reason this effort is necessarily somewhat prelim- 

 inary. It has not been my aim to identif}' doubtful species or solve diffi- 

 cult questions concerning closely related woods but rather to see if the 

 wood structure possessed any ready means by which the species could be 

 easily identified giving accurate points of difference instead of the lumber- 

 man's "I know it by the looks of it." 



The idea was to study some of the trees of this State and carefully de- 

 scribe, compare all parts exclusive of the bark, and then if possible dis- 

 tinguish by mentioning some of the characteristic differences. The wood 

 was first examined with the unaided eye and its various qualities noted. 

 Then a haiid lens was used and the transverse, tangential and radial 

 sections gone over, and lastly the compound microscope was used for the 

 more minute details. 



The specimens were.such as could be obtained in the vicinity of Lansing 

 aided by a large number of standard mounted and named specimens put 

 up by Mr. Hough of Lowville, New York. This furnished a sufficient num- 

 ber of specimens to enable me to get a fair average of the specific charac- 

 ters on which to base conclusions. If much variation was found, more 

 duplicates were made from different individuals to ascertain as nearly as 

 possible the individual variation that might be expected, and to enable 

 me to ])ick out a typical specimen. 



This work soon brought out the fact that different parts of the tree 



