548 IOWA ACADEMY OF SCIENCE 



PSEUDOTSUGA MUCRONATA Sudw. Douglas Fir. 



Leaves flat, notched above and keeled below, % inch to l 1 ^ 

 inches long. 



Resin ducts, 2, lateral and touching epidermis on ventral side, 

 ducts lined with 2 layers of cells, lignified where touching 

 epidermis. 



Vascular bundle surrounded by a most pronounced bundle 

 sheath of lignified cells. Xylem bundles appearing as one, 

 cells below phloem and above xylem lignified. 



Hypodermal cells present in 1 to 3 layers along dorsal and ven- 

 tral midrib, heavily lignified. 



Epidermis cells mammillated, mammillation most pronounced on 

 ventral surface. 



Walls of parenchyma corrugated. 



Stomata on lower surface. 



Material from Campus and herbarium of Iowa State College; 

 Jamaica Plains, Massachusetts; University of Washington, 

 Seattle ; State House grounds, Sacramento, California ; and 

 University of California. 



Plate LII. 



Figure 1. — Section of leaf of Pseudotsuga mucronata. 



Figure 2. — Section through epidermis and stoma of leaf of 

 P. mucronata. 



Figure 3. — Section through resin duct of leaf of P. mucro- 

 nata. 



Figure 4. — Section through vascular cylinder of leaf of P. 

 mucronata. 



