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 5½° or about 380 miles. This north and south extension produces a milder climate in the southern part, but no fern of essentially southern distribution comes in except Polypodium 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 Wisconsin line in the extreme northwest part. As there is nothing in these extremes of elevation to effect material 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 boundary, 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 before they were so generally taken up for cultivation. The loss in the original fern-flora is slight in this regard when compared with that of flowering plants. As nearly all of the state is in the region of the glacial drift, the soil is influenced by this condition also. The ravines cut in the drift and in the underlying rock where it is reached, with their varying degrees of moisture and shade, show the greatest variety in fern-life, though a greater abundance of certain kinds may be found in woods and swamps. The prevailing rocks are limestone, but sandstones occur in some localities, especially along the Illinois and Rock rivers. These in some parts of the state, particularly in the coal measures, the area of which is large, may be interstratified with shales and slate. These rocks and the soils resulting from their disintegration and decomposition, taken in connection with those of the glacial drift, provide a fair range of edaphic conditions for the growth of ferns. It is evident that such as prefer a calcareous soil will be best represented, if any preference of this kind inheres in their nature.
It will be seen from the list that not quite one half (56) of the Pteridophytes accorded specific rank in “Gray’s New Manual of Botany” (115) are reported from this state. The genera are represented in larger proportion, 23 of the 31 given, or if Athyrium be separated, 24 of 32, or three-fourths of them. All the species of several of the smaller genera are found, up to three in the case of Osmunda, but all of none with species exceeding this number. The genus most fully represented is Equisetum, eight of the ten, or nine of eleven when E. robustum is given specific rank. To these must be added E. Ferrissii, not in the Manual.
Reliable data for the distribution of the ferns of the state are not very full. It is hoped that they may be made more complete by the co-operation of those into whose hands the list may fall. Many additions to the number of species can hardly be expected. Doubtless the state has been quite well explored in this respect. I find only two to add to those published by Patterson in 1876, Isoetes Butleri, described in 1878 from specimens found in Indian Territory (Oklahoma) but since found in this state, and Equisetum Ferrissii, a recent addition. The list is mainly a compilation made at the request of the editor of the Fern Bulletin. No special fitness for the task is claimed, since my personal knowledge of the region covered is almost wholly confined to five of the northeastern counties, Kankakee, Will, Cook, Dupage and Lake. Only casual trips of slight duration have been made to other places. The publication most relied on for the state at large is the “Catalogue of the Phaenogamous and vascular cryptogamous plants of Illinois,” H. N. Patterson, Oquauka, Ill., 1876. His catalogue of plants growing in the immediate vicinity of Oquauka has also been used. Friedrich Brendel’s “Flora Peoriana, Budapest, 1882,” (the German edition, but since given in English, I believe) has furnished some definite information for a district around the city of Peoria. The floras of H. H. Babcock and of Higley and Raddin for Chicago and vicinity have likewise been consulted, but as they respect territory mainly familiar to the writer, could be cited but little.
As explanatory of the plan followed I may state that I have first mentioned the localities or stations with which I am personally acquainted, and from which examples are in my herbarium unless very common throughout. Citations from Patterson’s catalogue for the state at large are entered in quotation marks followed by (P.). Where Peoria is given the authority is Brendel, where Oquauka, Patterson. A few have been furnished by V. H. Chase, who collected in Stark county and vicinity, and by Prof. Atwell of the Northwestern University, from data in the herbarium of the University.