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. 

 Lignumvitae: 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) Sclerenchyma, 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 



