THE FERN BULLETIN 



Vol. XX APRIL, 1912 No. 2 



THE FERN FLORA OF ILLINOIS. 



By E. J. Hill. 



The state of Illinois has an area of about 55,000 

 square miles. It lies between the parallels 37° and 

 42° 30', thus giving a length of 5^° or about 380 

 miles. This north and south extension produces a 

 milder climate in the southern part, but no fern of es- 

 sentially southern distribution comes in except Poly- 

 podium polypodioideS) though the two quill-worts of 

 the state are perhaps better placed under this head 

 also. It is the lowest of the north-central states in 

 average altitude, the mean above sea level being about 

 600 feet, varying from 300 feet at the junction of the 

 Ohio and Mississippi rivers to 1250 feet at the Wis- 

 consin line in the extreme northwest part. As there 

 is nothing in these extremes of elevation to effect ma- 

 terial changes of temperature due to altitude, its 

 floristic features are not much modified in respect of 

 this. Anything of this character must be ascribed to 

 local conditions, not general causes. Another factor 

 that affects its floristic features is the dominance of 

 prairie within its boundry, the forests and woodlands, 

 sometimes very narrow strips, chiefly bordering its 

 streams and lakes. Since lands covered with grass are 

 not adapted to the growth of ferns, and consequently 

 are limited in species, their number and variety must be 

 much restricted for this reason. This must have been 

 the case in the primitive condition of the prairies be- 

 fore they were so generally taken up for cultivation. 



