EXERCISE XIV. 

 THE WHEAT PLANT. 



Supplies for a Laboratory Section of Twelve. From six to twelve specimens of wheat plants showing roots. 

 stems and leaves; some tap rooted plant such as the radish or beet; twenty-four heads of some common wheat. 



Part A. Characteristics of the Stem, Leaves, and Roots. 



1. Observe the stem or culm of a wheat plant, (a) Is it jointed? (b) Hollow or filled 

 with pith? The joints on the culm are nodes. The part of the culm lying between two joints 

 is known as an internode. (c) Draw a neat figure about natural size to show nodes and inter- 

 nodes of the wheat culm. 



2. The prominent parts of most leaves consist of petiole and blade. The petiole is the 

 part which joins the blade to the stem. In typical dicotyledonous plants it is usually a slender 

 stem-like structure, while the blade is broad and flat. Observe the leaves of the wheat plant. 

 The petiole of grass leaves, known as the sheath, is much flattened and forms a roll which 

 tightly clasps the culm. The blade is that part which hangs out quite free from the culm. 

 Between the blade and sheath lies a sort of joint. This "joint" appears to be stronger and 

 more dense than adjoining parts of the sheath and blade, (a) Observe the position of the 

 leaves along the culm. Are they opposite or do they alternate with one another? (b) 

 Leaves in general are divided into two principal groups as to the manner in which they are 

 veined — Parallel veined, as in the case of wheat, corn, blue grass, etc.,; netted veined, as in the 

 case of beans, beets and radishes. Make a neat drawing of a wheat leaf, showing the prin- 

 cipal parts and the manner in which it is veined, (c) Make a neat drawing of some netted 

 veined leaf, (d) Summarize the characteristics of a grass leaf. 



3. Observe the root system of wheat, (a) Does the wheat plant have a long main root 

 which extends vertically downward? The root system of wheat may be described as fibrous. 

 Corn, oats, blue grass, and many other plants have a fibrous root system, (b) Recall the ap- 

 pearance of the root system of a radish or a beet. These plants have what is called a tuber- 

 ous tap root Make a drawing of the root system of some tap-rooted plant. 



4. (a) What are the principal characteristics of a grass as brought out in this study? 

 (b) Name at least five common plants which you know to have these characteristics. 



Part B. The Inflorescence. 



5. The flowering region or inflorescence of the wheat plant is called in common speech a 

 "head," but in botanical language a spike. Notice that the groups of flowers are distributed 

 along a common axis. This central, zigzag portion of the culm is known as the rachis. The 

 flowers, you will notice, appear to have no foot-stock or pedicle. Such flowers are said to be 

 sessile. Name at least three other plants which appear to have sessile flowers on a central 

 axis. 



6. Figures 9. 10, 11 and 12, page 36, illustrate the gross structure of the wheat spike, (a) 

 Observe figures 9 and 11, which illustrate the spikelet side and furrow side of the wheat spike. 

 Which side is broader? (b) Observe a sample of wheat with which you are provided. Which 

 side is broader? 



.. figures 10 and 12, page 36. illustrate the rachis. Remove five or six spikelets from 

 near the base of the wheat spike which you have at hand. Observe (a) any tendency of the 



35 



