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A TEXT-BOOK OF BOTANY. 



A B 



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 tracheae (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 which are scattered the small 

 tracheae indicated by black dots. D, chestnut (Caslanea 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 (Ulmus 

 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. 



