48 NATURE TEACHING. 



are the medullary rays, which serve to main- 

 tain communication between the various parts. 

 By their means the water brought up by the 

 wood can be supplied to the cambium. 



5. If now a stem of sugar-cane, maize, 

 any palm, or indeed almost any other mono- 

 cotyledonous plant is examined, the parts will 

 be seen to be arranged in a vory different man- 

 ner to those of the stems already studied. In 

 the stems of this second set we can distinguish 

 no pith, no ring or column of wood, no separable 

 bark and no cambium. They exhibit in cross- 

 section a ground work of soft tissue in which 

 harder portions are irregularly scattered, and 

 whilst the outer portion forms a kind of rind it 

 is not essentially different from the rest, but 

 merely contains a much greater proportion of 

 the hard portions and very little of the soft 

 ground tissue. On cutting such a stem length- 

 wise it is readily seen that the hard portions 

 are in reality fibrous strands which run through 

 the stem. 



6. For a full description of the various 

 tissues composing these two types of stems the 

 reader is referred to botanical text-booksl 



