Family 4. GLEICHENIACEAE 
By WILLIAM RaLPH MAxoNn 
Mainly xerophilous plants of tropical and subtropical regions, mostly with 
branched and creeping rhizomes (erect in Stromatopteris), the fronds circinate 
in vernation, continuous with the rhizome, distant or subfasciculate, rarely 
simple, mostly consisting of an erect or ascending primary leaf-axis of inde- 
terminate growth bearing one or several pairs of opposite primary lateral 
branches in acropetal succession, these simple and determinate or 1 to several 
times dichotomous, the included (apparently terminal) buds dormant or devel- 
oping secondary or tertiary leaf-axes similar to the primary, the ultimate 
branches (pinnae) usually in pairs, bipinnate, pinnate or deeply pinnatifid, 
the segments or pinnules mostly elongate aud pectinate (or, in Gleichenia, 
minute, rounded or oval, and moniliform); veins free, once or several times 
forked (or, in Gleichenia, simple). Sori borne upon the under surface of the 
segments, dorsal upon the veins (or, in Gleichenia, terminal), superficial, non- 
indusiate ; sporangia sessile, subglobose to pyriform, usually 2-6, radial from 
a slightly elevated roundish (or, in Stvomatofteris, hippocrepiform ) receptacle, 
or in a few species numerous and borne in more than one rank; annulus 
obliquely transverse, nearly complete, the sporangium opening by a vertical 
fissure on the side facing the center of the sorus; spores diplanate or tripla- 
nate, smoothish or sculptured. Prothallia flattish, green. 
1. DICRANOPTERIS Bernh. Neues Jour. Bot. 
Schrad. 17: 38. 1806. 
Mertensia Willd. Sv. Vet.-Akad. Handl. II. 25: 163. 1804. Not Mertensia Roth, 1793. 
Mesosorus Hassk. Obs. Bot. Fil. Bogor.1: 2. 1856. 
Characters of the family, excluding those assigned to the old-world genera Gleichenia 
and Stromatopteris. 
Type species, Polypodium dichotomum Thunb. = D. linearis (Burm.) Underw. 
Primary branches bipinnate, the rachis not forked. 1. D. Bancroftiz. 
Primary branches mostly once or several times forked and wholly or par- 
tially pectinate, or rarely simple and pectinate. 
Internodes of primary branches naked normally. . 
A pair of accessory pinnae borne at all but the ultimate nodes. 2. D. flexuosa. 
Accessory pinnae wanting. : : 
Primary branches bilaterally asymmetrical, a falsely sympodial 
secondary axis formed by the unequal production of the naked ; 
alternate branches. ; 3. D. pectinata, 
Primary branches bilaterally symmetrical as to branches. __ 
Primary branches once-forked, the terminal bud abortive ; 
rachis flexuous; pinuules distant. . 4. D. retroflexa. 
Primary branches 2-3-forked, a secondary leaf-axis often ; 
developed; rachis straight ; segments close. 5. D. pleridella. 
Internodes (some or all) of primary branches at least partially pectinate. 
Primary branches simple or once-forked, wholly pectinate. 
Pinnules rigidly herbaceous, distant, conspicuously surcurrent. 6. D. orthoclada. 
Segments coriaceous or subcoriaceous, contiguous, slightly dila- 
tate. 
Segments linear, 2.5-3.5 cm. long ; veins 20-40 pairs. 7. D. trachyrhizoma. 
Segments broader, 1-2.5 cm. long; veins 15-20 pairs. 8. D. intermedia. 
Primary branches mostly 1-4-forked, at least some of the internodes 
partially naked. 
VoLUME 16, PaRT 1, 1909] 53 
