16 



STEM. 



89. The vascular system of Coniferous stems is 

 very destitute of true spirals, and their woody tissue 

 chiefly consists of that peculiar fibre we mentioned 

 before, (15.) 



Monocotyledonous and Endogenous Stems. 



90. On making a section of a stem of this division, 

 instead of finding a central cellular system or pith, 

 around which is concentrically arranged a vascular and 

 fibrous one in close connection with each other, tra- 

 versed by medullary rays, and harder at the centre 

 than the circumference, as we saw in the other, we 

 find the following : 



Fig. 10. 



9 1 . There is a uniform mass of cellular tissue filling 

 the stem, through which distinct bundles of woody fibre, 

 encircling vascular tissue, are seen running down, but 

 which are riot closely connected with each other, the 

 whole being enclosed in many cases within a mere epi- 

 dermis, but in others perhaps within a modified bark ; 

 the whole of the structure being harder at the circum- 

 ference than it is at the centre. 



