52 GROWTH AND WORK OF PLANTS 



projection at the junction of blade and sheath, and it partly 

 surrounds the stem. 



91. Gross structure of the corn stem as seen in cross 

 section. The outer hard layer is called the rind. The soft 

 pithy portion of the interior forms the bulk of the stem. Scat- 

 tered in the pith are minute firmer and more compact points as 



Fig. 50. 

 Broken corn stalk, showing nbro-vascular bundles. 



seen in cross section. In old corn stalks which have lain in the 

 field during winter and a part of the following season, if cut 

 through the rind with a knife and the pith within broken, these 

 firm portions are apt to pull out in the form of fibers as shown 

 in fig. 50. "Stalks" of celery (the petioles of the leaves) are 

 excellent to show these bundles which make old or tough celery 

 " stringy." 



92. Fibro-vascular bundles. These fibrous portions are 

 made up of several kinds of elongated cells united in the form of 

 a bundle. Some of the cells are slender, have thick walls, and 

 overlapping ends. They are woody fibers and give strength to 

 the bundle. There are other elongated cells which are tubular 

 and are joined end to end to form vessels. There are other kinds 

 of cells too, but the bundle takes its name from these two sorts 

 and is called a fibro-vascular bundle. The water which passes 

 from the roots to the leaves largely passes through these vessels, 



