118 LABORATORY AND FIELD EXERCISES 



(c-) Cambium. Is there any evidence of a cambium 

 composed of regular cells as in higher plants ? 



(d) Endodermis. A dark-brown layer surrounding 

 the phloem, beneath which is a single cell 

 layer containing starch, called the pericycle. 



(Y) Does the leaf trace have the same structure as 

 the main vascular cylinder ? 



(3) Drawing. Make a cellular drawing of a small por- 



tion of the main vascular cylinder, or of the leaf 

 trace to show the structure of the tissue elements. 

 Label correctly. 



(4) Summary. Summarize the distinctive features of 



the tissue arrangements in the fern as compared 

 with that of herbaceous dicotyledons. See the 

 summary of the anatomy of herbaceous stems in 

 Part I of the text. 

 9. Anatomy of eagle fern (Pteris aquilind). 



a. Gross anatomy. Study transverse sections of the eagle 



fern, as indicated above for Adiantum, using a hand 



lens first and then low powers of the microscope. 



Compare the main tissue layers with those of the 



maidenhair fern. 



(1) Epidermis and cortex. Are both epidermis and cor- 



tex present, and do they have the same cell char- 

 acteristics as in the maidenhair fern ? Is there 

 an exoskeleton in Pteris? 



(2) Vascular ring. Study the vascular system carefully 



with a hand lens and low power. Is there any- 

 thing corresponding to the single vascular ring of 

 Adiantum ? What kinds of tissue masses occupy 

 the pith region ? Do you find central skeletal, or 

 strengthening, masses and vascular strands ? See 

 text discussion of the eagle fern (Pteris aquilina). 



