MACROSCOPIC STRUCTURE. 39 



Genus Picea, species of spruce. The sapwood of moderate 

 breadth, the heart wood contains no colouring matter so that 

 after the sapwood has died, the sapwood and heartwood assume 

 the same tint and remain similarly coloured. The sapwood is 

 characterized by an exudation of turpentine, as in all woods 

 belonging to this type. 



Genus Pinus (Pinaster type). The Pinaster pines are 

 two-needled, with a moderately wide sapwood and slightly 

 reddish-brown heartwood, which becomes darker after felling. 

 The resin-ducts are somewhat larger than in spruces, and a 

 sudden transition of spring-wood into summer-wood is com- 

 moner in these pines. 



Genus Pinus (Taeda type), three-needle pines. Sapwood 

 v; i liable in breadth, heartwood as in Pinaster pines, but 

 resin-ducts larger and more distinct than in the latter (Fig. 23, 

 wood of Pinus galustris, pitchpine). There is usually a more 

 sudden transition into the, broad, hard, reddish summer-wood 

 than with Pinaster pines, to which section our Central and 

 Northern European pines belong. 



Genus Larix. Species of larch with narrow pale sapwood 

 and reddish-brown heartwood. The resin-ducts are always 

 liner and less numerous than in all the above-mentioned species. 



Genus Pseudotsuga. Spn-irsof l)ouglus-iir. The sapwood 

 is fairly broad, the heartwood reddish-brown, as in larch, and 

 cannot be distinguished externally from larch hearlwood. 

 For a certain diagnosis of the wood of all the above species 

 the use of the microscope is necessary, and exhibits such great 

 differences in the anatomy of the medullary rays, the resin- 

 ducts, and in PseudotsK<j<i, also in the tracheids, which (as was 

 shown by Somerville) have, like yew, spiral thickenings, 

 that no possible confusion can arise. 



31. Cembran pinewood (Pinus, sections Cembra and Strobus). 



(There are eight species of the Cembran type and eight of the 

 \Yeyniouth type in Europe, Asia and America.) 



The resin-ducts on all the sections are more distinct 

 than in the Pinaster pines, but less so than in the Taeda 

 pines. The transition from the spring-wood to summer-wood 



