84 



FOUNDATIONS OP BOTANY 



bundle of a leaf. This fact being known to the student would lead 

 him to expect to find the bundles bending out of a vertical position 

 more at the nodes than elsewhere. Can this be seen in the stem 

 examined ? 



Observe the enlai-gement and thickening at the nodes, and split 

 one of these lengthvrise to show the tissue within it. 



Compare with- the corn-stem a piece of palmetto and a piece of 

 cat-brier (^Smilax rotundifoUa, S. hispida, etc.), and notice the simi- 

 larity of structure, except for the fact that the tissue in the palmetto 

 and the cat-brier which answers to the pith of the corn-stem is much 

 darker colored and harder than corn-stem pith. Compare also a piece 

 of rattan and of bamboo. 



97. Minute Structure. — Cut a thin cross-section of the corn-stem, 

 examine with a low power of the microscope, and note : 



(a) The rind (not true bark), composed largely of hard, thick- 

 walled dead cells, known as sclerenchyma fibers. 



(6) The fibro-yascular bundles. Where are they most abundant ? 

 least abundant ? 



(c) The pith, occupying the intervals between the fibro-vascular 

 bundles. 



Study the bundles in various portions of the section and notice 

 particularly whether some are more porous than others. Explain. 

 Sketch some of the outer and some of the 

 inner ones. 



A more complicated kind of monocoty- 

 ledonons stem-structure can be studied to 

 advantage in the surgeons' splints cut from 

 yucca-stems and sold by dealers in surgical 

 supplies. 



Fio. 53. -Diagrammatic ^^- Mcchanical Function of the 

 Cross-Section of stem of Manner -of Distribution of Material 



Bulrusli i^Seirptis), a 

 Hollow Cylinder witli 

 Strengthening Fibers. 



in Monocotyledonous Stems. — The 

 well-known strength and lightness of 

 the straw of our smaller grains and of rods of cane or 

 bamboo are due to their form. It can readily be shown 



