326 PRACTICAL BOTANY 



upper limit into teeth, the number of which varies on 

 different axes. 



3. The internodes are marked by projecting longi- 

 tudinal ridges, which may be traced upwards into the 

 leaf-sheath, and are then seen to be continuous to the 

 apices of the teeth : between the ridges are depressed 

 channels. 



4. The lateral branches are always inserted at the 

 nodes, and at the base of the leaf-sheaths : note that 

 they are arranged in whorls, and appear to burst through 

 and rupture the leaf-sheath near to its point of insertion 

 on the axis, and at points alternating with the pro- 

 jecting ridges, i.e. at the channels. 



5. The roots (to be clearly distinguished from the 

 underground root-stock, which shows an alternation of 

 nodes and internodes as above described) are thin and 

 fibrous, and branch monopodially : they are inserted 

 with a whorled arrangement at the nodes, immediately 

 below the point of insertion of the lateral buds. The 

 underground stems and the roots are covered ex- 

 ternally by numerous fine root-hairs of a brown 

 colour. 



6. Note that at many of the nodes the lateral branches, 

 or the roots, or both, may be partially suppressed, their 

 development being arrested at an early stage : also that 

 frequently the basal internode of lateral shoots attached 

 to the nodes of the root-stock may be much distended, 

 while its apical bud is arrested : in some cases more 

 than one internode may take part in this development, 

 the result being a monilifonn structure : the tubers 

 thus formed are reservoirs of reserve material, and 

 being easily separated from the parent plant, they 



