STRUCTURE OF THE STEM 
103 
-113. Comparison of the Monocotyledonous and the Dicotyledonous 
Stem.! 
General Structure. 
Structure of 
Bundles. 
Growth in Thick- 
ness. 
MoNnOCOTYLEDONOUS 
STEM 
A hard rind of 
rather uniform struc- 
ture. Bundles inter- 
mixed with the pith. 
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. 
114. Review Sketches and Diagrams. 
DICOTYLEDONOUS 
STEM 
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. 
(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. 
