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A TEXT-BOOK OF BOTANY. 



RETICULATED TRACHEA and those with spherical or oblique slit 



pores are known as POROUS TRACHEA or vessels (Figs. 142-144). 



In those vessels in which but few of the transverse walls are 



obliterated, the walls are marked by both simple and bordered 



FIG. 144. Types of tracheae or vessels. A, vessels with annular and spiral thickenings 

 in Phlox Carolina; B, longitudinal section through fibrovascular bundle in aconite, showing 

 porous (p) and spiral tracheae (t), bast fibers (b), and some of the collenchyma cells (c); 

 C, longitudinal section showing reticulate tracheae in scopolia; D, longitudinal section of 

 the woody part of the rhizome of Spigelia, showing tracheae (t), tracheids (h), tracheae (r) 

 with yellowish-brown, gum-like masses; E, portion of xylem of stem showing in Hyos- 

 cyamus tracheae (t) with bordered pores and wood fibers (w), with simple oblique pores. 



pores, which latter are described under tracheids. Vessels contain 

 water, water-vapor, and air; in some cases they contain sugar, 

 tannin, mucilage, or resin. 



