Douglas Fir Fiber 675 



known as a resin canal, are found more or less commonly in the 

 wood. The cells forming the wall of the resin canal are different 

 in structure from the ordinary tracheids and usually are shorter. 

 As a result, an extremely short fiber may rarely be found in any 

 annual ring but could not be considered as a real minimum of the 

 tracheids of that ring. Resin canals also appear in certain of the 

 rays, but are not considered at all in this discussion. 



Under exceptional conditions, apparently when the wood is 

 compressed as it is forming, the fibers develop remarkably heavy 

 walls. Because of the reddish color this type of wood has been 

 named ' ' rotholz . ' ' The single tracheid from such an area may be 

 recognized by the spiral striations (not to be confused with the 

 tertiary, spiral thickenings referred to above), which appear to 

 represent the method in which the walls of the tracheid are formed. 

 (Plate 1, Fig. 3.) The pits in such a tracheid usually exhibit 

 long, slit -like openings, and the walls themselves seem often to 

 be spirally split. According to Shepard and Bailey (1) and Miss 

 Gerry (J) the fibers are shorter in the "rotholz" than in the same 

 annual ring where " rotholz " does not occiu*. We measured one 

 case in which the fibers in the "rotholz" averaged to be 3.3 mm 

 long, while those in the "zugholz" of the same ring were 4.51 mm. 

 Since this agrees with condition found in various woods by other 

 investigators, we made no further determinations. It may be 

 noted here that spring tracheids occtirring in "rotholz" ordi- 

 narily do not show the typical spiral thickenings which occur in 

 the normal fiber. 



Material 



All measurements included in this study were made on Douglas 

 fir trees from British Colimibia, one set being referred to as 

 shipment 2, the other as shipment 3. In referring to trees the 

 shipment number and tree number will be stated, thus 2-1 means 

 shipment 2, tree number 1, and 3-10 means shipment 3, tree nimi- 

 ber 10, etc. The following data is taken from the collector's 

 notes. 



Shipment 2, taken as typical of the so-called Coast type, came 

 from Abottsford, B. C; 100 feet above sea level; soil high class 

 agricultural type, a well drained sandy-clay loam 4 feet deep 

 underlaid with gravel; rainfall about 60 inches per year, the 

 stand of timber was close, 75 per cent Douglas fir, 22 per cent hem- 

 lock and 3 per cent cedar, timber cut from 60 to 70 M feet, board 



