58 CONTEIBUTIONS FROM THE NATIONAL HERBARIUM. 



3. Dryopteris simulata Davenp. Massachusetts fern. 

 Woodland swamps; Hollywood Swamp and near Suitland; reported also from one or 



two other stations. Late summer. Me. to central N. Y. and Md. 



4. Dryopteris thelypteris (L.) A. Gray. Marsh fern. 

 Marshes and low thickets, especially along streams; common. Midsummer. 



Eastern N. Amer. (Aspidium thelypteris Swartz. ) 



5. Dryopteris marginalis (L.) A. Gray. Marginal shield-fern. 

 Rocky hillsides in rich woods; common, chiefly along the upper Potomac. July. 



N. S. to Br. Col., south to Ga. and Okla. (Aspidium. marginale Swartz.) 



6. Dryopteris cristata (L.) A. Gray. 



Swamps and moist or boggy woods; common. July. Newf. to Va. and Ark., north- 

 westward. {Aspidium cristatum Swartz; A. filix-vias of Ward's Flora.) 



7. Dryopteris goldiana (Hook.) A. Gray. Goldie's fern'. 

 Rich deciduous woods; several stations along the upper Potomac, both sides; rare. 



N. Br. to Minn, and N. C. (Aspidium goldianum Hook. ) 



8. Dryopteris clintoniana (D. C. Eaton) Dowell. Clinton's fern. 

 Boggy woods; Lincolnia; very rare. Me. to Wis., south to N. 0. (D. cristata 



clintoniana D. C. Eaton.) 



9. Dryopteris boottii (Tuckerm.) Underw. Boott's fern. 

 Moist wooded ravines; several localities, mostly in runs of the upper Potomac. 



Summer. N. S. to Minn, and Va. (Aspidium boottii Tuckerm.) 



Now usually regarded as a hybrid between D. cristata and D. intermedia. 



10. Dryopteris spinulosa (Muell.) Kuntze. 



Rich low woods; common throughout the range. Summer. Newf. to Va., north- 

 westward. (Aspidium spinulosum Muell.) 



11. Dryopteris intermedia (Willd.) A. Gray. Wood fern. 

 Moist or dryish woods; fairly common. Summer. Newf. to Wis., south to N. C. 



(Aspidium spinulosum intermedium. D. C. Eaton.) 

 Besides Dryopteris boottii the following hybrids have been collected: 

 Dryopteris cristata X "marginalis Davenp. Two collections, near Great Falls, 



Va. (Dornell). 

 Dryopteris goldiana X marginalis Dowell. Woods near Kensington (Doiuell). 



Marsilea quadrifolia L. was accidentally introduced in 1880 at Government Fish 

 Ponds, since filled; it has perhaps escaped to the river. Native of Eur. and Asia; 

 possibly native at Bantam Lake, Conn., thence widely introduced from Mass. to Md. 



5. EQUISETACEAE. Horsetail Family. 



1. EQUISETUM L. 



Stems annual and of two kinds, the fertile appearing in spring and early withering, 



the sterile ones with whorls of numerous branches 1. E. arvense. 



Stems perennial, evergreen, alike, without whorls of branches 2. E. praealtum. 



1. Equisetum arvense L. Horsetail. 

 Sandy or alluvial soil; common. Early spring. Temperate N. Amer. generally, 



north of Mex.; also in Eur. and Asia. 



2. Equisetum praealtum Raf. Scouring-rush. 

 Alluvial banks of the Potomac and tributary streams; occasional patches, but not 



common. U. S. generally. (E. robustum A. Br.; E. hyemale of Ward's Flora.) 



