THE SEEDLING AND YOUNG PLANT. 



61 



sp. 



f 



p.v. 



FIG. 16. The various chief elements of the wood of the oak, isolated by 

 maceration, and highly magnified. /, a fiber, distinguished by its 

 thick vails, simple slit-like pits, and no contents ; w..p, part of a row 

 of wood-parenchyma cells, with simple pits, and containing starch in 

 winter ; tr, a tracheid, distinguished from the fiber especially by its 

 bordered pits ; p.v, part of a rather large pitted vessel, made up of 

 communicating segments, each of which corresponds to a tracheid, 

 and has bordered pits on its walls ; sp, part of a spiral vessel. 



