44 



Trees, Stars, and Birds 



iiils 



these vessels are visible as 

 open pores in the ends of a 

 piece of one of these woods. 

 The summerwood of these 

 trees has fewer tracheae 

 than the springwood, and 

 they are of smaller size. 

 Such woods are called ring- 

 porous; in them the large 

 tracheae are arranged 

 chiefly in rings in the 

 springwood. 



Maple, birch, and bass- 

 wood are diffuse-porous ; 

 that is, the vessels are 

 scattered through both the 

 springwood and summer- 

 wood. Is it easier to count 

 the rings in ring-porous 

 wood or diffuse-porous 

 wood ? Why ? Diffuse- 

 porous woods are of more 



even texture than the ring-porous kinds. What 

 diffuse-porous wood that we have studied is extensively 

 used for flooring? 



Pines and other conifers have no tracheae and their 

 woods are classed as non- porous (page 109). Yet annual 

 rings may be clearly seen in a piece of pine. The sum- 

 mer tracheids are narrower and thicker walled, making 



1 All the photographs of microscopic sections of woods shown in this 

 book are magnified 10 diameters. 



U. S. Forest Service 



FIG. 27. Cypress wood as it appears 

 under the microscope. The annual 

 rings in woods like cypress, pine, and 

 cedar are very noticeable, but there 

 are no large open pores and they are 

 classed as non-porous woods. 1 



