68 



BOTANY: PRINCIPLES AND PROBLEMS 



gated, water-conducting cells, the tracheids and duds, which dis- 

 tribute the water and dissolved substances brought up through 

 the stem from the root; and the bast, consisting of especially 

 modified cells, the sieve-tuhes, which collect from the mesophyll 



Chloroplas-f 



Nucleu 



Fig. 36. — A palisade-cell. The chloroplasts are somewhat biscuit-shaped 

 bodies, being roughly circular in face-view and elliptical when seen from the side. 

 They are embedded in the thin and transparent layer of cytoi)lasm, their broad 

 faces parallel to the cell wall. The chloroplasts which here appear circular are 

 therefore lying against the front wall, nearest the observer. Those which appear 

 elliptical are lying next the side walls. 



the food manufactured there and convey it to the bast of the 

 stem, along which it is transported to other parts of the 

 plant. 



The petiole, usually circular in cross section, has within it a 

 cylinder or half-cylinder of fibro-vascular bundles which are con- 



