264 Double Cross-Grain 



Remaining Species. 



All the remaining species were examined by the method of radial 

 fracture alone. In no case was any type of cross-grain discovered which 

 did not agree in essentials with that which is characteristic of the species 

 examined in detail. 



Even in the straight-grained Albizzia procera, slight variations in 

 the grain, too small to be investigated by the detailed method, could 

 be detected which conformed to the same general laws which applied to 

 Shorea robusla, etc. 



In Fig. IV, of the Plate, are shown the fractures obtained in a 

 portion of the transverse disc of Holoptelea iniegrifolia and> in Fig. V, 

 the fractures in the longitudinal series of sticks. 



General Considerations. 



During the course of this investigation several points stood out with 

 sufficient prominence to merit a short discussion anent their probable 

 significance. 



The wide distribution of double cross-grain and the uniformity of 

 its character among trees of the most diverse natural orders suggest that 

 it is the expression of some peculiarity common to a large circle of 

 affinity in the vegetable kingdom. 



The long series of intermediate forms between straight grain and the 

 full expression of double cross-grain reached by the serpentine cross- 

 grain of Shorea robusla and the probable double spiral of Calophyllum, 

 and the variation in its development among the members of the same 

 family (see Fig. 1), suggest that there is something, whether of internal 

 or external nature, that inhibits or enhances the expression of double 

 cross-grain, but for the formation of a correct judgment on this point, 

 research is necessary on the influence of local conditions of soil and climate 

 on the development of this type of grain. 



There may be, possibly, some correlation between a hot climate and 

 the prevalence of this type of grain, but this can only remain a supposition 

 until temperate climate trees and a larger number of trees from hot 

 climates have been examined from this point of view. 



In the attempt to place double cross-gram in proper perspective with 

 reference to other phenomena shown by living objects, a close similarity 

 was found to exist between the changes in the inclination of the grain 

 and the phenomenon of periodicity. 



Periodic phenomena among living organisms can be classed under 



