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A TEXT-BOOK OF BOTANY. 



A B 



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Fig. 200. Coarse structure of a number of woods as seen with a Coddington lens: 

 A, English walnut {Juglans regia) showing the tracheae evenly distributed in the form of 

 pores, which can be seen in the wood with the naked eye; the medullary rays are rather 

 faint and arranged in closely radiating, parallel rows; in the fall wood are numerous fine 

 transverse lines parallel with the annular markings. B. shell-bark hickory {Carya ovata) 

 showing a row of large trachea; (g) in the summer wood and somewhat smaller tracheae (g') 

 scattered throughout the subsequent growth; medullary rays numerous, as are also the 

 somewhat undulating transverse lines (F). C, white or canoe birch {Betula pendula) showing 

 distinct annular rings and numerous medullary rays between v.hich are scattered the small 

 tracheae indicated by black dots. D, chestnut {Castanea dentata) showing large tracheae 

 arranged in circular groups, those of the successive layers being smaller and arranged some- 

 what obliquely, forming triangular groups; medullary rays very faint; E, Elm {Ulmns 

 campestris) showing tracheae arranged in circles in the summer wood and in the later growth 

 a number of broad more or less undulating plates composed of very small tracheae; medullary 

 rays quite distinct; F, Cherry (Prunus domestica) , tracheae quite distinct in the summer 

 wood, forming several circular rows; medullary rays broad and distinct. — B, after Wiesner; 

 the remainder after R. Hartig. 



