A MANUAL OF BOTANY 130 



stem is commonly called a root.) Observe the direction of 

 growth, the size and color of the terminal growing part 

 {apical bud), and the roots ; also the place where the roots 

 of the present year were or arc attached. The leaves are 

 produced at nodes, and between the nodes are internodes. 

 What evidence do you find that indicates an age of more 

 than one year for the rhizome ? Why is the growth hori- 

 zontal ? Why are there not buds at both ends ? Do you 

 find any scales (rudimentary leaves) on the stem ? Why 

 are the stems of ferns living in cold regions underground 

 structures ? 



Cross section of rhizome. Examine (Ijii) a cross section of 

 the Pteris (brake) rhizome and observe carefully the four 

 tissues (cells similar in form, having the same use). What 

 color and form have the cells of the outside layer ? What 

 is the size of the cells ? This layer is the epidermis. Study 

 the cells next within the epidermis and occupying most of 

 the section. What color, form, and size have these cells? 

 Parenchyma or fundamental tissue ? 



Is the color everywhere the same ? Observe two dark 

 brown bands of cells (hard tissue) toward the center of the 

 section. What form has each band and what size, shape, 

 and thickness of wall have the cells ? Observe the remain- 

 ing tissue looking like round or oblong, lacelike areas scat- 

 tered here and there about the bands of hard tissue. This 

 tissue is the vascular tissue, and each area is a vascular 

 bundle. Each bundle is inclosed in a necklace of cells 

 (bundle sheath, endoderm) within which are wood cells 

 {xylem) and vessels (phloem or bast). Study a long section 

 through the same rhizome and try to locate the above tissues. 

 How do the cells differ in shape from the same cell in cross 

 section ? Seek to discover the use of each part of the vas- 

 cular bundles. 



Leaf structure. Examine (Jp) the veins in a loaf, and ob- 

 serve their method of branching, and whether the ends are 



