APPENDIX. 



471 



conspicuous resin passages, lined by a layer of epithelium 

 cells which secrete the resin; and the wavy surface of the 

 section (the ridges being the leaf -bases) is covered by a very 

 distinct epidermis and cuticle. Narrow resin ducts are 

 present in the wood of the bundles. 



TERMINAL BUD 



-- YOUNG CONE 



SHOOT OF 

 PRESENT YEAR 



. YOUNG 

 DWARF-SHOOT 



FOLIAGE 

 LEAVES 



SHOOT OF 

 LAST YEAR 



MALE 

 FLOWERS 



3*?. YEAR 



Fig. 10. Branch of Pine cut in May. 

 Most of the older dwarf -shoots and foliage leaves removed. 



The conducting tissues of the Pine stem are simpler in 

 structure than in the case of a Dicotyledon, and presents 

 some characteristic features. The wood contains no true 

 vessels, or continuous tubes formed by fusion of rows of 

 cells, but consists of long tapering cells resembling fibres in 

 form, but showing various forms of thickening. In the 

 innermost part of the wood, these structures, called tracheids, 

 bear spiral and ring-shaped thickenings, but in the secondary 

 wood each tracheid bears on its two radial faces (the 



