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.