FERNS OF THE DISTRICT OF COLUMBIA 45 
ATHYRIUM PYCNOCARPON (SPRENG.) TIDESTROM. 
Moist, cool woods and shaded, alluvial banks; a few 
localities in Rock Creek Park and along the Potomac. 
(Asplenium angustifolium Michx.) 
ATHYRIUM THELYPTEROIDES (Micux.) Desv. Moist, 
rich woods, mainly in alluvial situations; fairly com- 
mon, especially along the upper Potomac. .(Aspleniwm 
acrostichoides Swartz.) 
ATHYRIUM ASPLENIOIDES (Micux.) Desv. Low woods, 
and moist thickets; abundant. (Athyrium filix-femina 
of most American writers, in part. 
DryYOPTERIS HEXAGONOPTERA (Micux.) C. Cur. 
Dryish or well-drained deciduous woods; abundant; 
especially luxuriant in the rich woods of the upper 
Potomac, on the Virginia side. 
DRYOPTERIS NOVEBORACENSIS (L.) A. Gray. Moist, 
low woods and thickets; abundant throughout. 
DRYOPTERIS SIMULATA DavENP. Woodland swamps; 
Hollywood Swamp and near Suitland, Maryland; 
probably occurs also in — similar situations below 
the fall line. Late sum 
DRYOPTERIS <apans (L.) A. Gray. 
stream banks, and low thickets; common 
DRYOPTERIS MARGINALIS (L.) A. es Talus slopes 
and rocky hillsides in rich woods; common, chiefly 
along the upper Potomac. 
Dryopreris crisTaTA (L.) A. Guar. Swamps and 
moist or boggy thickets or thin woods; common. 
Dryoprerts GoipiANaA (Hoox.) A. GRay. Rich, 
deciduous woods; several stations along the upper 
Potomac, on both sides; rare. 
Dryoprerts Ciurnrontana (D. C. Eaton) DOWELL. 
Boggy woods; very rare; a single station (Lincolnia, 
Virginia). 
x Dryopteris Boorriu (TucKERM.) UNpERW. Moist, 
wooded ravines; several localities, mostly in “runs” of 
the upper Potomac. 
Marshes, 
