1 8 ANATOMY AND PHYSIOLOGY 



(g) The leaf -base, the portion by which the leaf is 

 attached to the branch. 



(h) If present, the stipules, outgrowths of the leaf- 

 base. Leaves without stipules are exstipulate. 



(i) Before the next class exercise compare with the 

 leaf studied, as directed above, various other 

 types of leaves collected by yourself, making 

 full drawings and notes. 



B. Anatomy of the Leaf: 



THE LOWER EPIDERMIS 1 



1. As directed by the instructor, remove a strip of 

 the lower epidermis of a foliage-leaf, and mount 

 it in water or clearing fluid, being sure to have the 

 outer surface uppermost. Record the name of 

 the species. 



2. Note the cellular structure of the epidermis. A 

 group of cells, similar in structure and function, 

 is called a tissue. The leaf-epidermis is epidermal 

 tissue. The cell-wall forms a box, having depth as 

 well as length and breadth. Note that you see 

 only the edges of the vertical walls. How many 

 are there? Are there other walls? If so, how 

 many? Are they visible? Explain. Make a dia- 

 gram of an epidermal cell as seen in perspective. 

 Are the cell- walls transparent or opaque? Give 

 a reason for your answer. Suggest the advantage 

 of this feature to the plant. 



3. Observe the somewhat lenticular openings, or 

 pores, each surrounded by crescent-shaped cells. 



1 Miss ECKERSON (Bot. Gaz., 46: 221-224. 81908) has recommended 

 the leaves of the following plants as specially satisfactory for the study 

 of the epidermis and stomata: Sunflower, Fuchsia speciosa, zonal Gera- 

 mium, and Tradescantia zebrina. 



