236 



INTRODUCTION. 



[part ii. 



If the leaf of a ^lonocotyledonous plant be 

 held up to the light, the principal veins will be 

 found to form parallel lines of nearly equal 

 thickness, the central one being very little, if any, 

 larger than the others 

 (see a in Jig. 108). 

 The trees belonging to 

 this division are all 

 natives of the tropics, 

 and their softest and 

 newest wood is in the 

 ' centre, where fresh de- 

 posits are made every 

 year inside the old 

 wood ; and hence, these 

 trees are called endo- 

 gens, which signifies, to 

 increase from within. 

 The wood of these trees 

 has neither medullary rays nor concentric rings ; 

 and a section of it appears pierced with nume- 

 rous holes (Z>), as may be seen by cutting off a 

 slice of bamboo. The germination of a Mono- 

 cotyledonous plant, with the cotyledon remain- 

 ing in the ground, is shown at c. 



The Dicotyledones and the Monocotyledones 

 have all visible flowers, and are hence called 

 Phanerogamse ; but the Acotyledones have no 

 visible flow^ers, and they are hence called Cryp- 



FjG. 103. — MoXOCOTYLEDOXOtri 



Plant. 



