ENDOGENOUS OE MONOCOTYLEDONOUS PLANTS. 165 



Plants of this kind compose the greater part of our 

 European trees, and their leaves have nerves much branched 

 and running into each other. 



ENDOGENOUS OE MONOCOTTLEDONOUS STEUCTUEE. In 

 the cane, neither bark, nor pith, nor wood, nor medullary 

 rays, are distinguishable ; but a transverse section of a stem 

 exhibits a large number of holes, irregularly arranged, and 

 caused by the section of vessel-like tissue, and the mass of 

 woody or cellular substance in which they lie embedded 

 (fig. 101). 



FIG. 101. Transverse section of monocotyledonous wood 



A longitudinal section exhibits similar differences, as in 

 figs. 102, 103. 



Plants of this latter class, are called endogenous, from 

 cvftov, within, and ycwaa), to increase, because their growth 

 takes place from within, from the centre to the circumference; 



HIKi Mr 



FIG. 102. 



Longitudinal section of 

 dicotyledonous wood. 



FIG. 103. 



Longitudinal section of mono- 

 cotyledonous wood. 



they are also styled monocotyledonous, because the germ has 

 but one cotyledon, or seed-leaf (fig. 104). 



Trees of this class prevail most abundantly in tropical 

 climates, and the nerves of their leaves run parallel to each 

 other. So constant are the characters of the two kinds 

 of venation in the leaves, that an experienced botanist, 

 on inspecting the fragment of a leaf, is able to distinguish 



