INTRODUCTION 



slow, perhaps as little as r V of an inch per annum, whilst its 

 near relative the White Elm is enabled to put on as much 

 as half an inch in the same time, and seldom less than inch. 

 If the White Elm were planted upon rocky ground it would 

 probably produce timber almost identical with that of the Rock 

 Elm. 



One or two details concerning the ring are useful, viz., the con- 

 tour, whether regular, waved (Fig. 122), toothed (Fig. 57), etc., 

 and the boundary, which may be formed by a fine line of 

 dense Autumn wood (Fig. 34), a line of contrast between the 

 lax wood of Spring following upon the dense wood of Autumn 

 (most Conifers, Deal, etc.) (Fig. 212), or a similar contrast formed 

 by a pore-ring in the Spring wood (Elm, Ash, Oak), or the 

 boundary may fail as already shown in the case of the Green- 

 heart. It is vague in the Oriental Plane-tree (Fig. 115), and 

 provides a ready means of distinguishing- that wood from the 

 wood of the Western Plane-tree (Fig. 114). This latter wood 

 has particularly clearly defined, dense, narrow boundaries to 

 the rings. 



It must be carefully borne in mind, however, that the 

 boundaries of the rings of woods like the Oriental Plane-tree 

 may be very clear at times, and can vary much in the same piece 

 of wood. Nordlinger uses this feature, the definiteness or indefinite- 

 ness of the ring boundary, as one of the chief divisions in his key 

 to the species in his wonderful book of sections. This is a fatal 

 blemish to that otherwise monumental work, and makes his 

 key almost impossible to use. Care must always be taken to 

 avoid confusing bands of pigment with the annual rings. In 

 the Rosewoods the black zones are usually concentric, and 

 only on close examination are they found to be out of har- 

 mony with the structure. A good illustration can be seen in 

 Olive wood (Fig. 86), so commonly made up in Birmingham 

 into mementoes of the Holy Land, in which wood the black 

 zones are always eccentric to a great degree. A curious and 

 beautiful wood from British Guiana, called Hoobooballi (Fig. 55), 

 exhibits these dark zones in a very unusual wavy form, the crest 

 of the waves of one circle meeting the hollows of the waves of 

 the next, so that the lines approach and recede from each other. 

 The Gimlet wood, from Western Australia (Eucalyptus salubris). 

 shows a somewhat similar arrangement, but here the true annual 

 rings behave in the s!*.me manner. The whole stem of this tree 

 is on the twist, and being three-lobed, or buttressed as it were, 

 gives rise to its appropriate popular name. 



The cut which passes through the centre of the tree in the 

 line of the pith presents a complete change of appearance, for 

 a feature which is not so conspicuous in the other sections is 



xiv 



