'2<>14 Journal of Applied Microscopy 



(b) Pteridiiini aquilinuni (L.) Kuhn. (Pteris). Eagle-fern. 

 Family, Polypodiacese. 



The eagle-fern grows on hillsides, especially in sunny places. The rhizomes 

 should be preserved in alcohol. 



1. Cut cross sections of the rhizome, mount, and sketch under dissecting 

 microscope, representing the following structures : the band of external scleren- 

 chyma, the pith or ground tissue, internal sclerenchyma in two large, brown 

 bands and in smaller patches, and the concentric hbro-vascular bundles — usually 

 three large ones and a number of smaller ones. Note the two lateral ridges. 

 How do you account for the dorsiventral condition of the rhizome? 



2. Under high power, make a careful drawing of one of the smaller vascu- 

 lar bundles, showing the bundle sheath (usually brown), the phloem and the cen- 

 tral xylem (wood). 



3. Test for starch with iodin solution. Draw some of the ground tissue, 

 showing the intercellular spaces, and starch in the cells. 



4. Draw a patch of cells from the internal and from the external scleren- 

 chyma, showing the thick cell walls. 



5. Cut longitudinal sections of the rhizome, mount and draw, comparing 

 the structures with those seen in the cross section. 



G. Describe the mode of growth of the Pteridium rhizome. What advantages 

 in the geophilous habit ? Has this rhizome any advantage over the vertical 

 rhizomes of Ophioglossum and Botrychium ? 



7. Carefully remove the leaves from the apex of a branch of the rhizome and 

 cut cross sections of the growing point. Mount the sections, and in the first 

 two or three look for the apical cell. Draw. Cut longitudinal sections of the 

 apex of another branch, mount and draw the section, showing the apical cell. 

 What is the shape of the apical cell ? 



S. Under dissecting microscope draw a leaflet of Pteridium from the lower 

 side, showing the membranous false indusium formed of the reflexed margin of 

 the leaflet. 



(c) Cyrtomin7n falcatiitn J. Sm. 

 Family, Polypodiacea. 



Cyrtomium grows readily in greenhouses and window gardens, and fresh 

 sporangia may be obtained at almost any time of the year. 



1. Examine a sterile leaf and a sporophyll. Draw one of the leaflets show- 

 ing the circular sori on the under side. 



2 Pick off some of the sori which have recently exposed the sporangia, ex- 

 amine and describe how the spores are scattered. 



3. Mount an indusium and some opened and unopened sporangia. Draw 

 the indusium under low power. 



4. Draw a single sporangium under high power, showing the stalk, annu- 

 lus, and lip cells. Contrast this sporangium with the one in Botrychium. Draw 

 some of the nonsexual spores. Note shape, color, and surface. 



5. Make a diagram in the notes showing the life cycle of a fern. See 

 Fig. 11. 



