32 LABORATORY AND FIELD EXERCISES 



accurately. Locate the rootcap if possible. Consult 

 the text on the parts of the root tip and label your 

 figure correctly. 



2. Cellular structure and cell growth of root tips. Select 

 prepared slides cut lengthwise through growing root 

 tips and study the cellular structure of the main root- 

 tip areas. 



a. Note the division of the root into an outer epidermal 



cell layer, a central axis cylinder, and an interme- 

 diate cortex, each composed of similar cell elements. 

 Consult the text figures and Fig. 11 on the structure 

 of the root tip. 



b. Rootcap. What is the character of the cells of the 



rootcap ? Do its cells differ at the extreme apex of 

 the root and at its upper border ? What is the geo- 

 metrical form of the rootcap ? How is it related to 

 the growing meristem cells and the growing cell 

 zones above it ? What is the function of the root- 

 cap ? How is it renewed when worn off by the soil ? 

 c. Meristem layer. What is the form and extent of the 

 meristem cell layer ? What are the distinctive char- 

 acteristics of its cells as regards size, form, and 

 cell contents ? Is the meristem a distinct layer of 

 cells or do its cells merge into the cells of the 

 rootcap below it and into those of the elongating 

 zone above it ? 



d. Elongating zone. Study the cells at the lower and upper 

 margins of the elongating zone. How do they differ 

 in these two regions from the cells in the central 

 region of the elongating zone ? Explain the changes 

 which you note in the cells of the elongating zone 

 from its lower to its upper margin. How are these 

 changes in the cells brought about? How is the 



