414 KANSAS ACADEMY OF SCIENCE. 



pores average 200 microns ; the micropores vary from 25 to 80 mi- 

 crons. The true cells, or microcells, are unusually large, about 21 

 microns. In chestnut the ducts are strongly oval in cross-section, 

 with the longer diameter radial to the tree, as usual in deciduous trees ; 

 the macropores measure 320 microns the shorter way and 400 the 

 longer way ; the micropores average about 50 microns. The cells are 

 20 microns, which is very large. 



In another group of trees the pores or ducts are all of one kind, 

 though manifestly there are great differences of size. As prominent 

 examples of one division of these may be cited maple, sycamore, Cot- 

 tonwood, and willow. In these the ducts are grouped into sets sepa- 

 rated by thin cellular walls or septa. The number of ducts in a group 

 varies from two to about five or six, seldom more. The distance be- 

 tween groups is usually much more than the breadth of a group. 

 These are close-grained woods. In maple the ducts seldom exceed 

 75 microns, and occupy apparently about one-ninth of the wood. In 

 sycamore the ducts are somewhat larger, but are crowded between the 

 very strong plates ; they occupy about one-seventh of the space of the 

 wood. In Cottonwood and willow the ducts are more uniformly dis- 

 tributed, are more numerous, and occupy about one-sixth of the wood. 

 As a distinction for this class of woods they will be called gamotra- 

 cheal. 



In a third group, which comprises all our fruit-trees and some 

 others, the ducts are all small, solitary, and very uniformly distributed. 

 These are our closest-grained woods. For distinction, they will be 

 called dialytracheal. In apple the ducts are elliptic to oval, measure 

 40 microns radially and four-fifths as much tangentially, and occupy 

 about one-eighth of the space. In cherry the ducts are SO to 60 mi- 

 crons, and occupy one-seventh to one-sixth of the space. In plum 

 the ducts are quite equidistant ; they vary in size from 30 to 50 mi- 

 crons tangentially and 30 to 60 radially, and occupy one-seventh of the 

 wood. The rays are strong in plum. In pear the ducts vary from 25 

 to 45 microns and occupy one- eighth of the space. The wood is 

 therefore about as close-grained and solid as apple wood. The cells 

 proper, which are exceedingly fine, not exceeding 12 to 14 microns, 

 are 1800 to 2100 to the linear inch, making possible 3,750,000 cells 

 to the square inch. But, as there are 50,000 ducts to the square 

 inch, occupying the space of ten times as many cells, it will be neces- 

 sary to deduct about half a million from this estimate, still leaving 

 3,250,000 cells and 50,000 ducts to the square inch. 



The rays or radial plates in the deciduous trees consist of strong, 

 thin, lenticular, horizontal, radial bundles of cylindrical, cylindroidal, 

 parallelepipedal, or even tabular cells placed on edge, and superposed 



