ECONOMIC WOODS OF THE UNITED STATES 



139 



transversely and arranged in a vertical series like the rungs of a 

 ladder. This scalariform pitting is characteristic of the vessels in 

 Magnolia, is common in Liriodendron and Nyssa, less so in Liqui- 

 dambar, Ilex and Platanus, and of sporadic occurrence in Castanea, 

 Castanopsis, Quercus, and some others. Since radial grouping is 

 the most common, the pitted surfaces usually appear to better 

 advantage in tangential than in radial sections. 



Pits between vessels and ray cells are simple on the ray side 

 but may be bordered, simple, or transitional on the other. These 



TABLE X 



NATURE OF PITTING OF VESSEL. WALL WHERE IN CONTACT WITH RAY 



PARENCHYMA 



* In Betula and Alnus the pits are bordered; in Carpinus, Corylus, and Ostrya 

 simple pits predominate. 



t In Rdbinia the pits are predominately simple. 



