538 
The Ohio Naturalist. 
[Vol. VI, No. 7. 
Thallus distinctly costate. Calyptra not surpassing the involucre. 
Antheridia on a separate thallus. 2. 
2. Divisions of thallus l>roadly linear, the margin mostly undulate 
crisped. cndiviacfolia Dumcrt. 
Divisions of thallus, the early ones linear-oblong, the margins 
ascending and remotely sinuate, the later ones linear-pinna- 
tifid. calycina Xees. 
Ptagiochila Dumort. 
1. Leaves with 3-12 large, spinulcse and distant teeth; no under- 
leaves. spimdosa Dumort. 
Leaves entire, repand or denticulate. 2. 
2. Lower part of stem leafy to the base; underleaves 2-3 ceft, fuga- 
cious. 3. 
Lower part of stem, forming a rhizome, bearing scales; no under- 
leaves; mouth of perianth ciliate. asplcnioides Dumcrt. 
3. Leaves entire or slightly repand; mouth of perianth crenulate. 
interrupta Dumcrt. 
Leaves entire, the uppermost repand-denticulate; mouth of peri- 
anth denticulate. porclloides Lindenb. 
Porclla Dill. 
1. Stems bipinnate; leaves more cr less remote, ovate-oblong, lower 
lobe minute, flat, as long but not half as wide as the ovate- 
rectangular entire underleav'es. pinuata L. 
Stems mostly simply pinnate (or bipinnate in P. platyphylla) ; 
leaves mostly closely imljricate, round— ovate cr ovate. 2. 
2. Leaves sub-erect, the straight ventral margin strongly involute 
towards the apex; cells punctate-stellifcrm. 
Sidlivantii Underw. 
Leaves flat or mere cr less concave at base cr somewhat conve.x, 
the margin decurved c r curved upwards. 3. 
3. L'jjper leaf-margin curved upwards and undulate, mostly entire; 
lower lobe reaching half of upper, hardly deuerrent; under- 
leaves semi-circular with strongly reflexed margins, entire. 
platyphylla Lindb. 
L^pper leaf margin decurved, mere or less denticulate; lower lobe 
smaller, long-decurrent ; underleaves subcrbicular or quad- 
rate-oval or quadrate, dentate cr ciliately serrate. 4. 
4. Underleaves suborbicular or quadrate-oval, the margins undu- 
late and dentate; lower lobe acute, reaching J of upper and 
half as wide as the dentate underleaves. dentata Lindb. 
Underleaves ejuadrate, the margins sparsely dentate; lower lobe 
oblong, obtuse, longer but narrower than the underleaves, 
both with stronglj- recurved and sparsely denticulate margins. 
Thuja Lindb. 
Preissia Xees. 
Thallus large, sparingly forking, increasing by joints, ends of lobes 
subcordate, with white pores above and dark purple scales 
below. Antheridia in a peduncled disk-like receptacle. 
Dioecious or usually monoecious. commutata Xees. 
Ptilidium Xees. 
Stem subpinnate with short rootlets; perianth several times longer 
than the involucre, .\ntheridia in the base of closely imbri- 
cated leaves. Dioecious. ciliarc Xees. 
Radula Dumort. 
1. Lower lobe small, rounded, more or less transversely adnate. 
tcuax Lindb. 
Lower lobe subquadrate, barely incumbent on the stem. 2. 
2. Widely subj>innately branched; leaves imbricate, rounded; peri- 
anth obconic, compres.sed. Antheridia in the bases of 2-3 
]>airs of stronglv imbricate tumid leaves, com planata Dumort. 
