TRILLIUM SP. 149 



b. The central cylindrical mass of cells, the plerome, that 

 finally becomes the fibrovascular bundle region or the 

 stele. 



c. Between the dermatogen and plerome is the periblem, 

 from which the cortex is finally developed. 



If the material is favorable, observe: 



4. The root-hairs. Observe on what part of the root they 

 are borne, also their relation to the epidermal cells. 



5. Diagram the regions observed. 



6. Make a transverse section of the root a litttle way back 

 from the tip, and identify the permanent regions mentioned 

 in the study of the longitudinal section. 



7. Diagram the transverse section. 



II. THE APICAL BUD or THE RHIZOME. 



Divide the tip longitudinally and on the cut surface observe: 



1. The shape. 



2. The sheathing membranous scales. 



3. Beneath the scales the small growing point of the stem. 

 On this may sometimes be seen rudimentary scales. 



4. In some such sections one may also see the base of rudi- 

 mentary branches. 



5. Diagram the section. 



III. THE AERIAL STEM.* 



Make a transverse section and observe: 



1. The single row of epidermal cells. Note the form of the 

 cells and the thickness of their walls. 



2. The large loosely arranged tissue with intercellular spaces, 

 the parenchyma. 



a. The shape of the cells. 



b. Relative thickness of the walls. 



c. Intercellular spaces. 



1 It may be found advisable to use instead of the section of a Trillium 

 stem that of corn (Zea mais) or some other Monocotyledon. 



