184 FIELD OATS. 



which increase in size toward the parenchyma, but do 

 not merge into it. Draw. 



6. The chlorofhyll-bearing parenchyma. Note 



a. The shape, size and arrangement of the cells. 



b. The thin walls. 



c. The contents ; protoplasm and chlorophyll bodies 

 which are green, if fresh stems are used. Notice 

 the position of the chlorophyll bodies. 8 



d. Draw a few cells. 



7. The fundamental parenchyma. Note the size and shape 

 of the cells, and the triangular intercellular spaces. 

 Draw a few cells. 



8. The fibro-vascular bundles. Notice the two series of 

 bundles : the larger ones nearer the central cavity of 

 the stem ; the smaller between the paired groups of 

 chlorophyll-bearing parenchyma. In the larger ob- 

 serve 



a. The external sheath, an irregular layer of cells, 

 with slightly thickened walls, 9 surrounding the 

 bundle, and thicker on its peripheral side. Exam- 

 ine it in a section from an older part of the stem ; 

 note the thickness of the walls. 



b. The tracheary tissue; on the right and left of the 

 bundle two large pitted vessels ; toward the axial 

 side one or two annular vessels j between the 

 large pitted vessels a transverse band of smaller 

 pitted vessels. 10 



c. Between the annular vessels and the external 



8 They may be made plainer by staining with magenta. 



9 If it can not be discerned, stain slightly with magenta ; these cells 

 take a deeper red than the rest. 



10 Stained a deeper red in the magenta-treated section. 



