96 PRACTICAL COURSE IN BOTANY 

 III. STEM STRUCTURE 



A. MONOCOTYLS 



MATERIAL. Fresh cornstalks with several well-developed nodes, 

 some of which should have stood in coloring fluid from 1 to 3 hours. If 

 fresh specimens cannot be obtained from the fields, a number of seedlings 

 may be grown in boxes of rich earth and cared for by the pupils either at 

 home or in the schoolroom ; they should be planted 4 or 5 weeks before 

 needed. Asparagus and smilax sprouts may be used, or the stem of any 

 large grass, or of wheat and other grains, but stalks of corn or sugar cane 

 make the best subjects for study where they can be obtained. 



APPLIANCES. A compound microscope will be needed for detailed 

 study. Prepared slides can be used, but it is better for students to make 

 their own sections where practicable. 



no. Gross anatomy of a monocotyl stem. Obtain a 

 fresh cornstalk, preferably one that has begun to tassel, - 

 and observe its external characters. How are the inter- 

 p nodes divided from one another ? What 



^ is the use of the very firm, smooth epider- 

 mis ? Notice a hollow, grooved channel 

 running down one side between the joints, 

 or nodes ; does it occur in all of them ? 

 FIG. 112. Cross Is it on the same side or on the opposite 

 r sides of alternate internodes? Follow one 

 cuiar bundles ; c, cor- of these grooves to the node from which 

 it originates ; what do you find there ? 

 After studying the internal structure of the stalk, you will 

 understand why this groove should occur on the side of an 

 internode bearing a bud or fruit. 



Cut a cross section midway between two nodes, and ob- 

 serve the composition of the interior ; of what does the bulk 

 of it appear to consist? Notice the arrangement of the 

 little dots, like the ends of cut-off threads, that are scattered 

 through the pith ; where are they most abundant, toward the 

 center or the circumference ? 



Make a vertical section through one of the nodes. Cut a 

 thin slice of the pith, hold it up to the light, and examine 



