APPENDIX IV 321 



vertical resin-ducts are few, but distinctly visible (Fig. 13), whilst the hori- 

 zontal ones are less easily seen. Two are probably visible on the right-hand 

 side of our plate. 



The Larch [Ldrix europc&a), (Plate XLV.), has a reddish-brown heart- 

 wood, well defined from tho yellowish sapwood which may extend through 

 from six to twenty years' growth. The rings are fairly broad, slightly undu- 

 lating in contour, and very sharply defined by the broad dark autumn zone. 

 The pith-rays resemble those of the Spruces. The resin-ducts are few in 

 number, and are often grouped in twos and threes. 



Pseudotsliga Dougldsu, variously, but not quite accurately, Imown as 

 Oregon Pine, Douglas Spruce, or Douglas Fir (Plate XL VI.), in many char- 

 acters, such as colour, definition of rings, and resin-ducts, much resembles 

 Larch. It is, however, usually of a rather more rosy red ; its vertical resin- 

 ducts are sometimes more clustered together, sometimes in Hnes of from eight 

 to thirty ; and horizontal ones are frequent. In a longitudinal section it can 

 be seen that the traoheids of the spring-wood are spirally thickened, whilst 

 those of the Larch are not. 



Whilst the highly resinous woods of the true Pines {Pinua) resemble those 

 of the Larch and Douglas in their well-defined heart and spring and autumn 

 zones, they are distinguished by the greater number and size of their resin- 

 ducts, which are distributed with considerable uniformity throughout the 

 rings. The knots in Pine wood, moreover, are generally approximately in 

 whorls, whilst those of Larch are irregularly distributed. As already stated 

 (p. 241), the Pines fall into two series, known as " hard " and " soft." The 

 former includes the Scots Fir, or Northern Pine {Pinus sylvestris), Corsican 

 (P. Laricio), and Cluster (P. Pinaster) Pines of Europe, and most of the North 

 American species, of which Pimis ^alustris, the Pitch Pine of English com- 

 merce (Plate XL VII.), may be taken as a type. Their greater hardness 

 and weight is generally indicated by a darker colour, ranging from yellow to 

 deep orange or brown, while their autumn-wood generally forms a considerable 

 proportion of the width of each ring, and is somewhat sharply marked off from 

 the spring-wood. Their resin-canals are chiefly in the autumn- wood. When 

 seen in radial section (Fig. 30), the tracheids of their pith-rays are seen to 

 have irregular tooth-Hke (" dentate ") projections. In the Pitch Pine — ^the 

 Long-leaved Pine, or Pensacola Pitch Pine of the United States — ^the resin- 

 ducts are comparatively few, and with such deHcate or imperfect epithelium 

 that they are commonly torn in section-cutting. Its rings are narrower 

 than those of most European Pines. 



The Soft Pines, on the other hand, of which Pinus Strobics, the Yellow Pine 

 of English commerce, the White Pine of its native North America, and the 

 Weymouth Pine of gardens (Plate XLVIIL), may be taken as a tjTpe, have 

 their greater softness indicated by their lighter colours, which range from 

 light-red to white. The zone of autumn-wood is narrow, and merges gradually 

 into the spring -wood on its inner margin. The resin-ducts occur ahke in 

 spring- and autumn- wood j and in the radial section no dentate projections 

 occur on the sides of the tracheids. 



