POLYPODIUM VULGARE 73 



() Is there a membranous expansion (indusium) 

 covering the sporangia in your specimen? Ex- 

 amine fronds of the other species of fern dis- 

 played in the laboratory and record your obser- 

 vations on this point, stating the names -of the 

 species observed. 



(0) Leaves bearing spores are sporophylls. Fern 

 leaves that do not bear spores are vegetative 

 leaves or foliage -leaves. 



(p) Do some of the sporophylls also function as 

 foliage-leaves? 



(q) Examine specimens of other kinds of ferns ex- 

 hibited in the laboratory and see if your answer 

 to (p) is true of all ferns. Describe briefly any 

 exceptions found, giving the name of the fern. 



(r) Make drawings, natural size, illustrating all 

 features of the frond not clearly shown in your 

 first sketch. 



D. Microscopic Characters: 

 i. The rhizome. 



(a) Study prepared slides of cross-sections of the 

 rhizome. (Pteris aquilina is suggested as spe- 

 cially satisfactory for this study, a-g.) 



(0) With the low power survey the section and 

 identify the various tissue-regions already dis- 

 tinguished. 



(c) With the high power, study the epidermis, and 

 describe how many cells it is in thickness, the 

 variation in thickness of the cell-walls, the 

 middle lamella, separating the adjacent cells, 

 and the canals, or channels, extending from the 

 cell-cavity outward through the cell-wall. Do 

 these canals ever branch? Do they form a 



