STEM. 17 



92. Now all stems having these characters are called 

 Endogenous or Monocotyledonous, and are to be found 

 in such plants as the Cane and the Lily. 



93. The cellular tissue of these stems, as in some of 

 the Palms, has sometimes its cellules very much deve- 

 loped towards the centre, and contains a considerable 

 quantity of amylaceous matter. 



94. The woody bundles do not always run down the 

 stem in a regular manner, but often cross each other 

 and go down obliquely, as in the Palms, and often ap- 

 proach very close together. 



95. In some of these stems, as in the Grasses, there is 

 a vacant place in the centre, and the woody bundles are 

 found all at the circumference ; originally this was not 

 the case. (For further considerations see physiology.) 



Acotyledonous Stems. 



96. Many of the lower tribes have no true axis at all, 

 their development being perfectly plane, as is seen in 

 many Lichens, Algae and allied plants ; in those, how- 

 ever, in which a sort of stalk or stem to such expansion 

 exists, the structure of it is merely cellular. In the 

 Fungi, the term stipes is applied to what otherwise 

 might be called their stem ; the structure is cellular. 

 It is in the foliaceous Mosses that a stem is first quite 

 evident, and here they are composed of cellular tissue, 

 the cells of which are elongated or cylindrical. In the 

 Ferns, the true stem of which is, in our country, gene- 

 rally below the ground, although in tropical ones rising 

 many feet above it, is composed both of cellular fibrous 

 and vascular tissue ; when cut across, bundles of woody 

 and vascular tissue are seen often very irregularly dis- 

 posed, which run down the stem : in some cases the 

 larger bundles are disposed cylindrically, and consist of 

 fibrous tissue containing within it both spiral vessels or 

 modifications of reticulated ducts. 



The appendages of the stem are now to be described. 

 c3 



