54 FOREST UTILIZATION 



Hemlock : Coarse rat-proof lumber ; dimension stuff and construc- 

 tion ; shingles; railroad ties; fencing; paper pulp; bark for 



tanning. 

 Douglas fir : All building lumber ; construction ; railroad ties ; 



trestle bridges; piles; car sills; ship building; masts; mining 



timber; bark sometimes used for tanning. 

 Firs : Paper pulp. In the East for corduroying. In the West for 



local lumber; packing cases; cooperage; interior finish; mine 



props. 

 Tamarack (Eastern) : Fence posts; telegraph poles; ship's knees; 



railroad ties. 

 Tamarack (Western): Posts; railroad ties; car construction; 



dimension stuff. 

 C. Tropical and subtropical timber. 



Yucca : Paper pulp and fibre for ropes ; pincushions. 

 Eucalyptus: Street paving; railroad ties; mine props; piles: ship 



building; wagon 'making; orchard paling. 

 Mangrove : Bark very rich in tannin. 

 Palmetto : Wharf piles ; pincushions ; brushes. 

 Lignttmvitae: Bowling balls; blocks for pulleys; fine interior 



finish and furniture; railroad ties in Panama. 

 Teak: Ship building and flooring; railroad cars; street paving. 

 West India cedar: Racing boats; cigar boxes. 

 Olivewood : ' Turnery ; inlaying ; furniture ; backs of hair brushes ; 



wood carving. The fruit yields the best oil for table use. 

 Quebracho: Tanning; paving; railroad ties. 

 Lancewood: Fishing rods. 

 Mahogany: Furniture; ship building; pianos; fine interior finish. 



XIV. TECHNICAL QUALITIES OF THE TREES. 



A. Botanical structure of the trees. 



I. Botanical structure of hardwoods. 



The cells forming the woody tissue are : 



(a) Ducts (pores, vessels) formed by the resorption of the 



partition walls in a vertically running string of cells. 

 Such ducts are characteristic of hardwoods. 



(b) Scl-erenchyma, cells of heavy walls and small lumina, 



usually forming long fibres. 



(c) Parenchyma, cells of thin walls and large lumina, fre- 



quently containing grains of starch. 

 Medulla or pith is found in the central column, in the 



primary, secondary, tertiary rays and (rarely) in 



medullary spots (birch). The central pith is: 



Heavy in ash, maple, elder, catalpa ; 



Triangular "in birch, alder; 



Quinquangular in hornbeam. 

 Broad leaved species are called "ring porous," if the 



spring wood of the annual ring contains strikingly 



