82 THE PLANT: A GENERAL INTERNAL VIEW 



These groups or bundles of xylem and phloem are called 

 the vascular bundles. You have frequently noticed vascu- 

 lar bundles even though you did not recognize them by 

 that name. When you eat celery which is a little too old 

 to be tender, it is the stringy vascular 

 bundles of it which get in your teeth. 

 When you peel a banana you are sure 

 to see vascular bundles. They either 

 come off with the skin or stick to the 

 pulp. If they stick to the pulp you 

 strip them off, for they are too tough 

 to eat. 



Many stems, however, are not dis- 

 tinctly hard in the outer part and 

 soft in the inner part like the stems 

 we have been describing. In some 

 stems you find no pith. Woody stems, 

 like the stems of trees and shrubs, 

 are hard all through. Such stems last 

 over winter and form new layers of 

 cuiar bundles are quite wood year by year. They do have 



distinct in this stem, ten of 1 i_ _n 1 • i_ j 



them being shown. Com- vascular bundles which are arranged 

 pare with Figure 24 in in a cylinder, but the arrangement is 

 which the bundles he made complex by the addition of new 



closely side by side. The L J 



tissue lying within the layers year by year. The arrange- 

 ring of the bundles is pith. men t of woody stems is discussed in 



(So also in Figure 24.) 



the chapter devoted to stems. 

 The stem of corn has still another arrangement. In it 

 the hard parts, the vascular bundles, are scattered through 

 the body of the stem. (See Figure 32.) They look in 

 the picture like islands lying in the sea of softer tissue. 

 Stems having this arrangement are common, but they 



Fig. 31. — Half of a cross 

 section of the stem of a 

 common plant. The vas- 



