FERNS OF THE District oF COLUMBIA 47 
EQUISETUM PRAEALTUM Rar. Alluvial banks of the 
Potomac and tributary streams; occasional patches, 
but not common. 
LYCOPODIACEAE 
Lycopopium LucipuLuM Micux. Damp woods and 
springy wooded banks, sometimes in beds of sphag- 
num; infrequent. 
Livchbonidik CAROLINIANUM L. Macaolu bogs; only 
a single locality known, in Prince George County, 
Maryland. 
LycopopiuM ADPRESSUM (CHApM.) Luoyp & UNpERW. 
Bogs and low, open fields, often in the shallow overflow 
of springs; abundant at several localities in the Coastal 
Plain. 
Lycopopium opscuruM L. Moist woods and thickets; 
a few scattering localities only. 
Lycopopium cLtavatuM L. Moist thickets and pine 
woods; rare; known only from three widely separated 
localities. 
LYcOPpopIUM COMPLANATUM FLABELLIFORME FE 
NALD. Pine woods and thickets, with Pyrola, Pidaés: 
phila, and Mitchella; fairly common. 
LycopopIUM TRISTACHYUM PursH. Damp pine woods 
and thickets; not uncommon. 
SELAGINELLACEAE 
SELAGINELLA RUPESTRIS (L.) SprinGc. Exposed rocky 
bluffs; found only in the vicinity of Great Falls, on 
both sides of the Potomac. 
SELAGINELLA Apopa (L.) FERNALD. Low, moist situa- 
tions, usually in partial shade; locally abundant, but 
very generally overlooked. (Selaginella apus Spring.) 
ISOETACEAE 
IsonTeEs ENGELMANNI VALIDA ENGELM. ‘Temporary 
pools among rocks; Virginia shore of the Potomac 
near Great Falls; very rare. 
