THE FILMY FERN IN ILLINOIS 
ROBERT A. EVERS * 
The filmy fern, Trichomanes boschianum Sturm, fig. 1, is one of the rare 
| ferns in North America, It is a perennial, evergreen plant with very slender, 
creeping, wirelike rootstocks and with fronds that have light green, translucent 
blades only one cell thick, This fern is amember of the filmy fern family, the Hyme- 
nophyllaceae, a family of more than 300 species, which occurs throughout the tropics 
and in New Zealand. One species occurs in central Europe. T. boschianum grows 
in southeastern North America, where it ranges from Alabama northward to West 
Virginia, Ohio, and southern Illinois. It apparently has a very restricted habitat; 
it requires, in most cases, moist, shaded, vertical faces at the bases of sandstone 
erhangs, 
With the destruction of our natural landscape to provide for more and wider 
highways and for more home sites, and with the construction of dams and the conse- 
quent flooding of large areas behind the dams to form artificial lakes, we donot know 
how long some of the habitats of our rare plants will remain intact, Therefore I 
have written this article to record for botanists and other interested persons the 
known locations of the rare filmy fern insouthern Illinois, I have recorded the infor - 
mation chronologically so that readers may experience vicariously the pleasure I 
perienced in my search for sites of the filmy fern, 
For many years the filmy fern was known to occur in southern Illinois ata 
station in Jackson Hollow in Pope County, fig. 2, locality 5. This knowledge was 
based uponcollections made on August 2, 1923, by Dr. Mary M, Steagall of Southern 
Illinois University, These collections are now in the herbarium of that university 
and the herbarium of the University of Illinois, The next knowncollections in Illinois 
were made more than a quarter of acentury later by Julius Swayne and myself, Mr, 
Swayne was at the time a student at Southern Illinois University and later at the Uni- 
versity of Illinois, Bailey & Swayne (1952) stated that this site was the one in which 
Dr, Steagall collected the fern; they wrote, ''Our collection [Swayne 1136] undoubted- 
ly is from the same location,'' Most botanists in Illinois have accepted this conclusion, 
and, as there is no evidence tothe contrary, I shall refer to this locality as the 
Suetercite, It is in the E 1/2, sec. 6, T. 125S., R. 5 E, 
In 1955 Franklin Buser, then a graduate student at the University of Illinois, 
now of East Stroudsburg, Pennsylvania, called to my attention an almost unknown 
article by Miss Helen M, Strong (192), who had been a student in one of the classes 
of Dr. H, C. Cowles of the University of Chicago. Miss Strong reported the oc- 
surrence of filmy fern (Trichomanes boschianum) on sandstone in Bethell Hollow in 
Pope County. After reading her article I became convinced (andI believe I convinced 
Mr. Buser) that Bethell Hollow and Jackson Hollow were the same place, The de- 
cription seemed to pertain to the Steagall site in Jackson Hollow; two of the plants 
Which Miss Strong listed for the Bethell Hollow station, neither of which is common 
in Illinois, namely, rattlesnake plantain (Goodyera pubescens) and "ground pine"' or 
lub moss (Lycopodium lucidulum), also were growing at the Jackson Hollow station. 
Miss Strong had not collected specimens from Bethell Hollow. 
; *Robert A. Evers is Associate Botanist, Illinois Natural History Survey, The photography is the 
work of William E, Clark, who visited all the known localities of the filmy fern in Illinois and took numer- 
us photographs of the sites and the ferns, Miss Marguerite Verley drew the map that is fig. 2. James S. 
Ayars edited the manuscript. Mrs. Betty Nelson typed the manuscript for reproduction. 
Fig. 1.--Delicate fronds of filmy fern growing on moist sandstone in the north section of Jackson 
Hollow, southwest of McCormick, Pope County. 
