DISTINCTIVE CHARACTERS 39 



student of converted timber. The annual rings by tlieir width 

 indicate the rate of growth, a character of great importance 

 as to quaUty, if not of great distinctive value. More than 12 

 rings to the inch, giving, as it does, 6 feet of girth in 134 years, 

 may be termed slow growth ; from 12 to 6 rings to the inch, 

 which would mean 6 feet of girth in from 134 to 67 years, 

 moderate ; and less than 6 rings to the inch, or 6 feet of girth in 

 67 years, jast growth. 



The absence of pores or vessels is characteristic of coniferous 

 woods. As to the size of pores, Mr. Gamble classifies them in 

 7 groups : extremely small, as in Box ; very small, as in Aotr 

 fictum ; small, as in Haldu {Adina cordi folia) ; moderate-sized, as 

 in Mahwa {Bdssia latifolia) ; large, as in Siris {Albizzia Lebhek) ; 

 very large, as in Erythrina suherosa ; and extremely large, as in 

 many climbers (Fig. 4, for instance). 



So too the pith-rays, as distinctive characters, are grouped 

 under seven types : extremely fine, as in Euonymus Idoerus ; very 

 fine, as in Ebony {Diospyros Melanoxylon) ; fine, as in Siris 

 (Albizzia Lebbek) ; moderately broad, as in Dillenia pentagyna 

 (Compare Fig. 34, p. 48) ; broad, as m Plane {Pldtanus orientdlis), 

 in which case they measure \ mm. ; very broad, as in some Oaks, 

 in which they reach 1 mm. ; and extremely broad, as in Samara 

 robusta. The number and distance apart of the pith-rays are also 

 characters of consequence. When further apart than twice the 

 diameter of the pores they may be termed distant 



There are some of these microscopic characters that are 

 eminently distinctive of large groups, such as the Natural Orders 

 into which botanists group plants. The Cupuliferce, for instance, 

 that great group to which the Oaks, Beeches, Chestnuts and 

 Hornbeams belong, have their pores in wavy radial lines or 

 queues : in the Mendcece, or Ebony tribe, and the jSapotdcece, a 

 closely-aUied tropical Order, including the Bullet- woods {Mimusops), 

 the pores are in short, wavy lines, and there are wavy false rings ; 

 but whilst the Ebendcece have white, grey or black wood, that of 

 the Sapotdcece is reddish. So too the tropical Order Anondcece, 

 or Custard-Apple family, which includes the Lancewood of the 

 West Indies, has regular ladder-like transverse bars on its woods 

 that are very characteristic. 



Several of the characters used in the classification of woods, 

 such as weight per cubic foot, hardness and amount of ash left on 

 combustion, not only vary together, but also differ according to 

 the age of the tree and the distance of the sample from the root. 

 Weight, for instance, increases from the butt to the lowest branch, 

 and decreases from the latter point upward. 



