6 PROPERTIES OF WOOD. 



Wavy lines of finer vessels and surrounding parenchyma 

 scarcely recognizable. 



6. The llolnnia or False Acacia (llolnnia). 



(This includes other Papilionaceae, such as Gleditsia, 

 Laburnum, etc.) 



Transverse Section. The pores in the spring- wood some- 

 what wider than in the summer-wood ; in the sapwood 

 (Fig. 15, left-hand) open, and therefore dark in the plate, 

 but closed by thyloses in the heartwood, so that they are 

 but slightly visible in the pale yellow spring- wood. The 

 vessels in the darker summer-wood are surrounded by 

 pale parenchyma, and appear as wavy or zigzag lines. 

 The spring-wood is pale and porous, so that the annual 

 rings are distinct. The medullary rays appear as pale, fine 

 lines. 



Radial Section. The borders of the annual rings are quite 

 distinct, owing to the open grooves of the vessels in the sap- 

 wood, and the pale zones of spring-wood in the heartwood. 

 The rays are distinct as bright, pale portions of bands. 

 The parenchyma of the summer-wood appears as bright 

 longitudinal lines. 



Tangential Section. The vessels of the sapwood and heart- 

 wood appear as in the radial section ; the parenchyma of the 

 summer-wood, as wavy bands parallel to the annual rings, 

 brighter or darker than the mass of the wood according to 

 the angle of incidence of light. 



Rotainia. The sapwood is narrow ; the heartwood light 

 yellowish-green, becoming later brownish-green. 



Gleditsia. Sapwood broad ; heartwood rose-coloured. 



Laburnum and Cladrastis. Very narrow sapwood ; heart- 

 wood reddish-brown. 



7. Species of Walnut (Julians). 

 (Represented by six species in America, Asia, and Europe.) 



Transverse Section. The pores are pretty evenly distri- 

 buted throughout the annual zones, but SOUK 'times more 



