J. F. Martley 261 



Although, as the transverse series shows, these compound periods 

 persist completely round at a transverse level, it seems that they are of 

 only limited longitudinal extent. 



CALOPHYLLUM 1 sp. POON. 



For the material of this species I am indebted to Professor Groom 

 for permission to saw a transverse section off each end of a six-foot beam 

 of Poon wood, 10 inches by 3 inches in section, the longest side of the 

 section being in a radial plane. 



The rings were counted on both sections and to ensure identity 

 in numbering every fifth ring was traced from end to end on the radial 

 surface of the beam. The ring nearest the centre was numbered 1 but it 

 was impossible to say how far it might have been from the centre, but 

 the shape of the rings indicated that the beam had been sawn from near 

 the outside of a very large trunk. 



The numbering of the rings on the two sections only approximately 

 correspond as difficulty was encountered in tracing the rings along the 

 beam due to the rings frequently fading away, although in many cases 

 they reappeared after a longer or shorter distance. 



In Table VII are given the data derived from a radial stick sawn 

 from each transverse section and the corresponding curves are shown in 

 Fig. 11. The rings were plotted natural width and not to a scale of 2 to 1 

 as for the other species. 



The striking feature of Poon wood is the great length of the period 

 (8| cms.), being a little more than twice that of Shorea robusta. In 

 another specimen of Poon, and probably of the same species, having the 

 same number, four, of rings per centimetre, the period length was 

 6 cms. This fact suggests that a study of double cross-grain with reference 

 to soil and climate would yield interesting results. 



If the rings are used as an index of contemporaneity, though this 

 is somewhat open to doubt for Poon wood, it is seen that the periodic 

 changes in the inclination of the grain are practically simultaneous 

 through a length of six feet, contrasting with the comparatively big 

 shift in the position of some of the periods of the longitudinal series of 

 Shorea robusta and Xylia dolabriformis. 



Judging from the contemporaneity of the periods and the slight 

 variation in their amplitude at the two levels it is to be inferred that the 

 grain in Poon is a true double spiral. 



1 The specific identity of the wood examined was doubtful, though it bore the name 

 of Poon, which belongs to Calophyllum tomentosum. 



