353 



variations. In India teak is used for railway sleepers, bridges, buildings 

 and furnitures. 



Teak is very fragrast wben fresh and resembles rosewood, owing to 

 an oleo-resin which also renders the wood probably the most durable of 

 known timbers, making it obnoxious to termites and keeping off rust from 

 iron in contact with it. Seasoned teak has, however, a very unpleasant 

 smell, which has been compared to that of old shoe-leather. It is distrib- 

 uted in India, Burma, Siam, Ceylon, Java, Sumatra, and Celebes. In the 

 Philippines small plantations occur in the southern islands, especially in 

 Zamboanga district, Basilan Island. 



RELATIONSHIP BETWEEN THE RESISTANCE AND THE PHYSICAL 

 PROPERTIES OF TIMBER 



It has been proved that some timbers are more highly re- 

 sistant to termite attack than others ; or, in other words, dur- 

 abihty of timber seems to be effected by its physical or chemical 

 properties. Determination of the factor of resistance is highly 

 important in order to discover the preventive measures against 

 termites. Therefore, the relation of the physical properties of 

 timbers to the resistance is considered first. 



Mancono and aranga, which are included in the group "very 

 hard," are more seriously attacked than ipil, molave, and ma- 

 caasim of the group "hard ;" banuyo is less attacked than harder 

 woods, such as palo maria, tindalo, etc. ; calantas, a soft wood, is 

 also less attacked than tucangcalao, amuguis, acle, etc.; which 

 belong to the group "hard." 



Ipil, molave. and macaasim, which are included in the group 

 "heavy," are less attacked than very heavy mancono ; that dungon, 

 bansalaguin, batitinan, etc., are more seriously attacked than 

 banuyo and palo maria of the group "moderately heavy;" and 

 that amuguis, acle, guijo, etc., are also more seriously attacked 

 than calantas, a light wood. 



Thus the durability or resistance of timbers to the attack^ of 

 termites is not effected by hardness or weight ; that is, the im- 

 munity of timbers is not due to their physical properties. 



RELATIONSHIP BETWEEN THE RESISTANCE AND THE CHEMICAL 

 PROPERTIES OF TIMBER 



Snyder ' states that the immunity or relative resistance of 

 ironwood is not due to hardness — since Asiatic termites attack 

 the hardest wood, lignum-vitae — but to the presence in the wood 

 of a substance (oils or alkaloids) repellent or distasteful to 

 termites. He also states that the presence of tyloses or of gums 

 may be factors in determining the durability and resistance of 

 hardwood species. It has been proved that the physical prop- 

 erties of woods are not the real factor of resistance as suggested 

 by that author. However, another suggestion of Snyder, that 

 the presence of certain chemical substances in woods is the 

 true factor, is somewhat dubious. As he gives no data in detail, 

 it is hard to understand what are the principal ingredients -and 

 how they act in preventing the damage. 



TBull. U. S. Bur. Ent. 94, (1916) 79, 80. 



