FUNCTIONS OF CONIFEROUS WOOD 



23 



of conifers, consisting, as it does, so largely of tracheids, it is these 

 tracheids, communicating as they do by the bordered pits on their 

 radial walls, that convey water and air from the roots to the leaves, 

 though they also store up starch in autumn and winter. The pith- 

 rays being elongated radially, retaining their protoplasm, forming 



Fig. 18.— Transverse section of part of young stem of Oak, highly magnified. 

 «&, pith ; c, cortex ; i, epidermis ; h, periderm ; g, coUenchyma ; r, spiral vessels 

 forming protoxylem ; pv, pitted vessels (trachea3) ; sm. secondary pith-rays ; p, wood- 

 parenchyma ; n, m, cambium ; k, bast-fibres. (After Hartig, from The Oak, by per- 

 mission of Professor Marshall Ward and Messrs. Kegan Paul, Trench, Trttbner & Co.) 



starch, and communicating through their pitted walls with phloem 

 and even cortex as well as xylem, undoubtedly play an important 

 part in the transfer of formative material from one part of the 

 stem to another. 



When we examine the stem of a broad-leaved tree, such as an 



