28 Jackson . — Anatomical Structure of the Roots of Barley . 
inches in length. The central region of the stele consists of thin-walled 
parenchyma, and in this root four large ducts are present, two of which are 
almost completely divided into two separate cavities, so that in the older 
part of the root six fully developed ducts are found. The xyl'em groups, 
each containing one large thickened vessel, are arranged in a circle outside 
that formed by the ducts. They are separated by thin-walled parenchyma, 
piliferous layer. 
cortex. 
Barley . 
part of a T.S.ofa 
Young "unbranched" root. fxio;J 
endodermis. 
pericyde. 
central duct. 
pa ren c hymat ous 
ground tissue. 
centra! duct. 
Fig. 6. 
the phloem at this stage not being differentiated from the rest of the ground 
tissue. The pericycle consists of typical radially elongated, and the 
endodermis of tangentially elongated cells, but in neither layer are any of 
the cell walls thickened. The cortex is composed of about seven rows 
of large parenchymatous cells, of which only the inner five rows are shown 
in the figure. The piliferous layer bounding the cortex also consists of 
parenchymatous cells rather elongated in the radial direction. 
Fully developed roots. A still older root presents the appearance 
