EXERCISE XIX. 

 THE CORN PLANT. 



Supplies for a Laboratory Section of Twelve. Six roots of the corn plant with about one foot of the stalk 

 attached. Six tassels of the corn plant with about two joints of the stalk attached Six ears w<<h about three inter- 

 nodes and leaves attached. Six specimens of ears removed from the stalk in such a manner as to leave shank and 

 husks attached to the ears. Six immature cars of pod, pop, flint, or sweet corn showing silks and jointed husks. 

 Ears or kernels "i pod corn. 



Part A. Stems, Roots, and Leaves. 



1. (a) Considering wheat to be a typical grass, what do you observe to be characteristic 

 of the steins of grasses? (b) Examine the culm (stalk) of a corn plant. Does it have the 

 essential characteristics of a true grass? (c) In what way does the corn stalk differ from that 

 of wheat? In gross internal structure? (d) In shape of cross section? 



2. Examine what is unquestionably a corn root, (a) In what particulars does its struc- 

 ture differ from that of a grass stem? (b) Examine the large centrally located part of the 

 corn plant which is below the surface of the ground. Split it so that you can examine its 

 structure. Is this part root or stem? (c) From what points along this centrally located part 

 do roots arise? (d) What term will describe the root system of the corn plant? 



3. Observe any evidence of roots arising from nodes above the surface of the ground, (a) 

 Of what use might above-ground roots be to the plant? (b) What, then, could above-. 



ground roots properly be called? 



4. There is a connecting part between the ear and the corn stalk, (a) From what point 

 on the stalk does this "connecting part" arise? (b) Does it appear that the shape of the 

 stalk at this point has been modified to accommodate this "connecting part"? (c) From 

 your study of the culm of the wheat plant can you see any reason why it need not have the 

 same shape as that of corn? (d) Split and examine the "connecting part." What points in 

 its structure identify it as a stem? (e) In general what name do we apply to a stem which 

 arises from a main stem? (f) Strictly speaking what, then, must we call the stem which con- 

 nects the ear with the main stem of the corn plant? (g) Count, if possible, the nodes in the 

 stem which supports the ear and compare with the number of nodes between the point of at- 

 tachment and the tassel, (h) What is the main difference between the internodes of the 

 "connecting part" and those of the main stem? (i) What does the farmer call this "connect- 

 ing part"? 



5. (a) From what points along the main stem of the corn plant do leaves arise? (b) 

 What are the two main parts of a grass leaf? 



Notice that in the grass leaf there is a sort of joint between the blade and sheath. 



6. (a) From what points on the stem supporting the ear, do husks arise? (b) Is the 

 arrangement of the husks along this short stem alternate or opposite? (c) Examine the outer 

 husks of the ears of some of the more primitive appearing corns such as pod corn, pop corn, 

 flint corn, or sweet corn. Do you find near the outer end of any of the husks a trace of a 

 "joint"? (d) From your observations what do husks really appear to be? (e) What evi- 

 dence can you give in support of your answer? 



7. (a) It is possible to think of all the separate parts which you have thus far studied 

 as branches of the main stem of the corn plant. Assuming these parts to be branches do they 

 have anything in common as to point of origin? (b) Illustrate. 



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