XL] STONEWORTS, AND PEPPERWORTS. 167 



the CharacecE, or Stoneworts. They have exceedingly 

 slender stems, but in spite of their slenderness and 

 brittleness they sometimes attain the length of three 

 or four feet. They are leafless, but, like Equisetum, 

 give off a whorl of branches from the nodes. The 

 plant is attached to the bottom of ponds and streams 



FIG. i?o. 



FIG. 121. 



by slender rootlets, which are also given off from the 

 nodes. The most remarkable feature of these plants 

 is the structure of the stem and branches. Each inter- 

 node consists of a large and long cell (axial cell), in- 

 vested by a number of spirally -arranged, smaller 

 and narrower cells (cortical cells), so transparent that 

 the axial cell can be seen through it. The axial cells 

 are separated at the nodes by a layer of smaller (nodal 

 cells), which is a continuation of the cortical layer. 



