138 



ECONOMIC WOODS OF THE UNITED STATES 



TABLE IX 



Indigenous Woods with Spiral Markings in Part or in All of 



the Vessels 



Ace race.*: 



Acer 

 Anacardiace.*: 



Cotinus 



Rhus 

 Anonace^; 



Asimina 

 Aqtjipoliace^! 



Ilex 



BETtlLACE^i 



Carpinus 

 Ostrya 



BlGNONIACEjE 



Catalpa 



BORAGINACE^S 



Ehretia 

 Cheiranthodendr^e 



Fremontodendron 

 Ericaceae 



Arbutus 



Arctostaphylos 



Andromeda 



Kalmia 



Oxydendrum 



Rhododendron 



Vaccinium 

 Hamamelidace.s: 



Liquidambar 

 Hd?pocastanace.e 



Msculus 

 Leguminos^e 



Cercis 



Gleditsia 



Gymnocladus 



Robinia 

 Leitneriace^e 



Leitneria 

 Magnoliace^e 



Magnolia 

 Meliace^; 



Melia (Nat.) 



MORACEiE 



Broussonetia (Nat.) 



Morus 



Toxylon 



OLEACE^i 



Chionanthus 

 Osmanthus 



Rhamnace^: 



Ceonothus 



Rhamnus 

 Rosacea 



Amelanchier 



Aronia 



Cercocarpus 



Prunus 



Pyrus (in part) 



Rosa 



Sorbus 



ScROPHULARIACE.dE 



Paulownia (Nat.) 



SlMARUBACE^E 



Ailanthus (Nat.) 

 Koeberlinia 



TlLIACE^! 



Tilia 

 Ulmace^! 

 Celtis 

 Ulmus 

 Planera 



The vessels of secondary wood are always pitted. (See pits, 

 p. 31.) This feature is seen to best advantage in macerated 

 material, especially where the vessels are so large that most of the 

 wall is cut away in sectioning. The nature of the pitting is de- 

 termined by the contiguous elements. The number, form, and 

 arrangement of the pits on a given area of wall depends upon the 

 particular kind of cell in contact there and the breadth of the sur- 

 face of contact. The character of the pitting between adjacent 

 vessels and between vessels and ray parenchyma is the most im- 

 portant for diagnostic purposes. , 



Pits between vessels are invariably bordered. The features 

 worthy of special notice are the arrangement of the pits, the size 

 and contour of the border, and the nature of the pit mouths. It 

 is very common to find vessels in groups so compressed that the 

 walls of mutual contact are flattened out broadly. In walls thus 

 flattened it is not uncommon to find pits that are greatly elongated 



