146 PROPERTIES OF WOOD. 



root-rot in conifers. Usually they are found only at the 

 lower end of logs. 



Violet-coloured streaks and bands penetrate the heart- 

 wood of many species of walnut, e.g., Juglans regia and 

 J. Sieloldii, instead of its being of the usually uniform brown 

 colour. These are not signs of decay but raise the value of 

 the wood, for the mottling of the wood may be due to alterna- 

 tions of colour as well as to ripples in its structure. The 

 woods of deciduous species of Diospyros, that grow in warm 

 temperate countries, have alternately dark and light grey 

 bands of wood. [Similarly, alternations of black, brown or 

 grey colour occur in the heartwood of numerous species of 

 Indian ebony-trees, the most striking of which are D. Kurzii 

 and D. quaesita,ihe latter yielding Calamander wood. Tr.] 



A bluish-green tint is assumed by the wood of all broad- 

 leaved and coniferous trees that are attacked by the fungus, 

 Peziza aeruginosa, this is chiefly the case with logs and 

 branches lying on the ground in moss or dead leaves. 



White streaks occur in the woods of oaks and other species 

 when attacked byStereum hirsutum&ud other fungi, and they are 

 then said to be white-piped. 



The white spots on a brown ground known as partridge- 

 wood, though Mayr says that the German word for this is 

 Rehbunt (fawn-coloured) and not Rebhuhn (partridge), is due to 

 Thelephora Perdix, the true name of which is said by Massie 

 to be Stereum frustulosum. Wood attacked by Trametes 

 Pini is spotted with white, and if by Fames annosus (Trametes 

 radiciperda), with black spots on a white ground. 



The red or greyish-brown coloured heartwood of beech, 

 termed also false heartwood of beech, has been investigated 

 by Mayr. He states that there are two kinds of this 

 abnormally coloured heartwood : 



Colouring-matter round the pith, which has possibly 

 a similar origin to the colouring-matter in the heart- 

 wood of other species and has similar properties, namely, 

 that of increasing its durability. When it appears in 

 irregular patches on a cross-section of the wood it is 

 prejudicial, as these patches can neither be stained nor 

 impregnated. 



