138 



ECONOMIC WOODS OF THE UNITED STATES 



TABLE IX 



Indigenous Woods with Spiral Markings in Part or in All of 

 the Vessels 



AcERACEiE 



Acer 



ANACARDIACEiE 



Cotinus 



Rhus 

 Anonace.e 



Asimina 

 Aquifoliace.e 



Ilex 

 Betulacejs 



Carpinus 



Ostrya 



BlGNONIACE^E 



Catalpa 



BORAGINACE^E 



Ehretia 



CHEIRANTHODENDR.E 



Fremontodendron 

 Ericaceae 

 Arbutus 

 Arctostaphylos 

 Andromeda 

 Kalmia 



Oxydendrum 

 Rhododendron 

 Vaccinium 

 Hamamelidace^e 



Liquidambar 



HlPPOCASTANACE^E 



Msculus 

 Leguminos^e 

 Cercis 

 Gleditsia 

 Gymnocladus 

 Robinia 



LEITNERIACE.E 



Leitneria 

 Magnoliace^e 



Magnolia 

 Meliace.e 



Melia (Nat.) 

 Morace^e 



Broussonetia (Nat.) 



Morus 



Toxylon 

 Oleace^e 



Chionanthus 



Osmanthus 



Rhamnace.e 



Ceonothus 



Rhamnus 

 Rosace.e 



Amelanchier 



Aronia 



Cercocarpus 



Prunus 



Pyrus (in part) 



Rosa 



Sorb us 



ScROPHULARL\CE.E 



Paulownia (Nat.) 



SlMARUBACE.E 



Ailanthus (Nat.) 



Koeberlinia 

 Tiliace.e 



Tilia 

 Ulmace.e 



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 



