CHAP, iv STEMS 21 



2. Detach one or two of the vascular bundles at one end 



and peel them away from the pith. Notice the 

 fibrous character of the bundle. (Very frequently 

 the hard bast is the only portion which will come 

 away from the pith.) 



3. Test the strength of a vascular bundle as compared with 



a piece of the pith. 



4. Make a sketch with notes to record these points. 



VI. The Sunflower stem is a good type of an exogenous 

 stem, or one which has the vascular bundles arranged in a 

 cylinder about a central pith. (In some plants the pith 

 disappears during growth and the stem becomes hollow.) 

 Plants with exogenous stems have netted-veined leaves, di- 

 or poly-cotyledonous embryos and the parts of the flower 

 usually arranged in fours or fives. 



VII. Take a piece of the stem of Indian Corn several 

 inches long, examine carefully and notice : 



1. The regular succession of nodes and internodes. 



2. The consistency of the stem (see I, 2, of this chapter). 



3. How long does the Corn stem live? 



4. Is it herbaceous or not? (see I, 4, of this chapter). 



5. Make a sketch of this piece of stem, representing and 



labelling the parts. 



VIII. Examine a thin transverse section of the stem of 

 Indian Corn in the way indicated in paragraph II of this 

 chapter. Notice : 



1. The vascular bundles. These are scattered through the 



pith, leaving no central portion free. 



2. The outer bundles We placed closer together and 



approach the outer edge very closely, but there is 



