FIG. 17. Transverse section of cortex and phloem of oak (highly 

 magnified), k, the periderm (cork), which has replaced the epi- 

 dermis ; c, collenchyma ; d, cells of cortex containing crystals of 

 oxalate of lime ; s, schlerenchyma cells. All these belong to the 

 cortex proper. Below these come the phloem : b, b, groups of hard 

 bast fibres ; bp, phloem-parenchyma ; bs, medullary ray ; e, cells 

 containing crystals of oxalate of lime. (Luerssen.) 



