PERSIMMON PINE. 275 



and are, therefore, invisible to the naked eye, but vary in depth, 

 having generally from three to eight radial rows of elements, of 

 which the central rows are parenchyma or cellulose walled cells, 

 with simple pits on their radial walls, i.e. on those in contact 

 with the tracheids of the xylem, whilst the upper and lower row 

 or two consist of tracheids with bordered pits. The rings are 

 rendered distinct by the darker and firmer zone of autumn wood 

 in each, consisting of more compressed, thicker-walled elements. 

 This simplicity of structure and resinous character renders the 

 wood uniform and even in texture, easy to work and of consider- 

 able durability. It is also on the whole soft, light, elastic, stiff, 

 and strong, characters which, coupled with its abundance in pure 

 forests forests, that is, mainly made up of a single species 

 combine to render the Pines the most generally useful and among 

 the cheapest of woods, 



The wood even of a single species of Pine varies very much, 

 according to the conditions under which it is grown; but, though 

 connected by intermediate cases, most of the species fall into two 

 fairly well-marked groups, known in America as the " Hard " and 

 " Soft " Pines. The Hard Pines are harder, heavier, and darker- 

 coloured, ranging from yellow to deep orange or brown : their 

 autumn wood forms a much broader proportion of the ring and is 

 somewhat abruptly marked off from the spring wood ; and the 

 tracheids of their pith-rays have their walls very unevenly 

 thickened with tooth-like projections. This group includes the 

 Northern (Pinus sylvtetris), Austrian (P. austrtaca), and Mountain 

 (P. montdna) of Europe, and the majority of the North American 

 species. The Soft Pines are softer and lighter; range in colour 

 from light red to white; have a narrow autumn zone gradually 

 merging into the spring wood on its inner surface; and have 

 smooth v/alls to the tracheids of their pith-rays, with no tooth-like 

 projections. The group includes the Cembra Pine (P. Ctmbra) 

 of Europe, and the White (P. Strdbus), Sugar (P. Lambertidna) and 

 a few other species in America. 



Pine seasons rapidly and with but little shrinkage, this being, 

 however, greater in the harder kinds: it is never too hard to nail; 



