INTRODUCTION 



which are always radially elongated, so that a radial section 

 makes them appear as broad grooves, whereas a tangential cut 

 will show but half their width. Confusion can easily arise in 

 practice from this cause, and no small demand is made upon the 

 imagination to reconcile the differences shown by an oval-pored 

 wood cut on the quarter (radial section), with its abundant 

 coarse grooves and showy " silver-grain," and another piece of 

 the same wood cut " plank-wise " (tangential section) on which 

 but few narrow pores and no " silver- grain " are to be seen. 

 The Horse-Chestnut (Fig. 32), the Box-tree (Fig. 105) and a great 

 number of others do not display any pores which are visible to 

 the naked eye, but it must not be concluded that the woods are 

 Coniferous because the pores are not thus visible. The lens 

 or even the microscope must be called in, when they will appear 

 as minute apertures or grooves as the case may be. No Broad- 

 leaved tree entirely lacks pores except a -very curious tree called 

 " Drimys chilensis " (Fig. 150), a relative of the Magnolias. 

 Its fellow species (Drimys winteri), the " Winter's bark," some- 

 times exhibits a few, not always (112). These are extraordinary 

 cases which are anomalous and require further study. Another 

 such is Acacia juniperina (Fig. 153), which closely resembles the 

 Coniferous type of wood inasmuch as it has a few isolated pores 

 in a loose ring here and there, quite unlike any other species of 

 Acacia (compare Fig. 43). It is interesting to note that a great 

 many climbers superficially resemble each other in their wood, 

 notwithstanding the fact that they may have no relation to 

 each other. All their pores are of great size and extremely 

 closely packed, and form" a tissue which looks like lace in a thin 

 section, but it is probable that if the pores were less over- 

 grown and numerous, the arrangement appropriate to the 

 genus would become apparent, because masses of crowded pores, 

 which leave little room for any woody tissue, must bear a com- 

 mon aspect in whatever order the pores arise. 



In all cases where the arrangement of the pores takes 

 definite form, such as festoons, tree-like or flame-shaped groups, 

 they strike the eye as an independent portion of the wood, 

 especially when they are compacted together into masses by 

 the " Soft-tissue " or short, thin-walled wood-cells (Woody 

 parenchyma). The commonest form of " soft-tissue " is a coat 

 of delicate cells which clothes the pores and appears as circles 

 round their orifices, or as borders by their sides in a vertical 

 section (plank-wise or quartered). If the latter sections be 

 in the least oblique, as is usually the case, the soft-tissue looks 

 like a tail or fringed continuation of the pore. Often the coat 

 of soft-tissue is so narrow that it is only by careful search 

 for these " continuations " that it can be detected. Inasmuch 



xxiv 



