276 TIMBERS AND THEIR USES 



to an orderly arrangement seems almost im- 

 possible. 



" It is not unnatural to assume that woods 

 possessing two kinds of rays should be grouped 

 apart from those having but one kind ; but by 

 separating them we cut off the Cupuhferse, the 

 Casuaerineae and the Proteaceae, and perhaps 

 many other orders yet unworked, from the 

 remainder of the broad-leaved trees, making an 

 artificial group of unrelated plants. Therefore 

 our classification cannot be based upon this 

 feature. The arrangement of the pores is very 

 characteristic of many orders, and is very con- 

 stant throughout long series of species, as the 

 Cupuliferee, the Myrtaceae, the Proteaceae and 

 the Urticaceae, but similar arrangements of the 

 pores can be found in quite unrelated orders. 



"Again, the soft tissue or wood parenchyma is 

 equally casual in its appearance, and, from the 

 study of Solereder's work, I conclude that the 

 minute structure of the wood, the pitting of the 

 cells, etc., is also unsuitable as a basis. 



" Any one of the various kinds of tissue may 

 be absent except the wood fibres and rays, and 

 the following alternatives may be found. 



1. Wood fibres and rays. 



2. "Wood fibres, rays and pores (vessels). 



3. Wood fibres, rays, pores and soft tissue 



(wood parenchyma). 



