68 



OF WOOD IN GENERAL. 



rending of trees by frost, the noise of which disturbs the stillness 

 of night in the forests of North America may in this way be 

 sometimes concentric in its action. This may explain the 

 prevalence of this defect in the swamp-loving Pitch Pine (Pinus 

 austrdlis) of Virginia. Frost cannot, however, be the cause of the 

 frequency of cup-shake in the tropical Lignum Vitae ; but in this 

 case the sun may have produced an effect similar to that which 

 sometimes occurs when part of the cambium ring at the base of a 

 stem is injured by a forest fire. Lastly, in some Pines this defect 



FIG. 39. Star-shake. 



is the result of the attacks of certain fungi (Tramdtes), the 

 " spawn " or " mycelium " of which spreads as a felted mass 

 of colourless mould especially in the cambium. Cup-shake 

 occurs most frequently at the base of the stem : when of long 

 standing, it is often accompanied by traces of rot, and in many 

 cases it is also associated with star-shake. 



Star-Shake. Star-shake consists in clefts radiating from the 

 pith along the planes of the pith-rays and widening outwards 

 (Fig. 39). 



It occurs in many species and in trees of all ages. The clefts 

 may only extend a small distance and be so slightly open when 



