STRUCTURE OF THE STEM 



103 



113. Comparison of the Monocotyledonous and the Dicotyledonous 



Stem. 1 



MONOCOTYLEDONOUS DICOTYLEDONOUS 



STEM STEM 



General Structure. 



A hard rind of 

 rather uniform struc- 

 ture. Bundles inter- 

 mixed with the pith. 



Structure of 

 Bundles. 



Growth in Thick- 

 ness. 



Bundles closed, 

 that is, without per- 

 manent cambium. 



Cells of mature 

 parts of stem expand 

 somewhat, but (in 

 most palms) new ones 

 are not found. 



A complex bark, 

 usually on young 

 shoots consisting of 

 a corky layer, a green 

 layer, and a layer of 

 bast. Wood in an- 

 nual rings. Pith in 

 a cylinder at the cen- 

 ter. 



Bundles open, with 

 permanent cambium. 



New wood-cells 

 formed throughout 

 growing season from 

 cambium ring. 



114. Review Sketches and Diagrams. 



(1) Monocotyledonous stem (lengthwise section). 



(2) Dicotyledonous stem (lengthwise section). 



(3) First appearance of bundles in dicotyledonous stem. 



(4) Dicotyledonous stem five years or more old (cross-section). 



(5) Various bark-cells. 



(6) Various cells from wood. 



(7) Pith-cells. 



(8) Collenchyma-cells. 



1 This comparison applies only to most of the woody or tree-like stems. 



