Order FILICALES 
By LuciIEN Marcus UNDERWOOD AND WILLIAM RaLPH Maxon 
Sporophytes terrestrial or epiphytic (or in one family aquatic), herbaceous 
to arboreous, consisting of a radicate creeping, ascending, or erect primary 
axis, the stem (rhizome or caudex), and more or less expanded leaves (fyonds), 
these minute to many meters long and of diverse form. Sporangia deyeloped 
normally from single epidermal cells (leptosporangiate),* variously disposed, 
mainly upon the under surface of the leaf, commonly in clusters (sori) upon 
the veins, or within special marginal indusia, or, less commonly, irregularly or 
in rows upon rachiform or scarcely foliose pinnae or segments. Indusia of 
various form, or wanting. 
Gametophytes normally in the form of green flattish or filamentous pro- 
thallia, each bearing both archegonia and antheridia (monoecious), or less com- 
monly these borne upon separate prothallia (dioecious). 
Sporangia sessile or short-stalked. 
Plants usually aquatic. 4 Fam. 2, CERATOPTERIDACEAE. 
Plants terrestrial or epiphytic. 
Sporangia not associated in definite sori, mostly (as to 
American species) borne upon rachiform or narrowly 
foliose pinnae or segments. 
Sporangia irregularly placed, provided with an incom- 
plete lateral annulus above the middle; plants meso- 
philous or hydrophilous. Fam. 1. OSMUNDACEAE, 
Sporangia borne in definite rows, provided with a com- 
plete subapical annulus; plants mainly xerophilous. Fam. 3. SCHIZAEACEAE. 
Sporangia usually associated in definite clusters (sori). 
Sori mostly borne upon the backs of the leaves or (by 
suppression of the leaf-tissue) marginal, the spo- 
rangia radial in one or several ranks upon definite 
receptacles arising from the veins or less commonly 
continuous with them. 
Sporangia stthglobose or obconic, relatively few, de- 
hiscing vertically, the sorus flattened; receptacle 
scarcely elevated. Fam. 4. GLEICHENIACEAE, 
Sporangia ovoid, very numerous, dehiscing horizon- 
tally, the sorus essentially globose ; receptacle con- 
siderably elevated. Fam. 5. CYATHEACEAE. 
Sori invariably marginal, terminal upon the modified 
elongate free ends of the veins (receptacles) within 
tubular or salverform indusia; leaf-tissue usually deli- 
cately membranous. Fam. 7. HYMENOPHYLLACEAE. 
Sporangia long-stalked. Fam. 6. POLYPODIACEAE. 
1In the Osmundaceae the origin of the sporangia is sometimes intermediate between 
the eusporangiate and leptosporangiate types. 
VOLUME 16, Part 1, 1909] 25 
