The Flora of the Cayuga Lake Basin 31 



In the borders of swamps where T. cristata occurs, plants are often found which 

 are more or less intermediate in character between T. cristata and T. spinulosa, var. 

 intermedia, and which are probably hybrids of these two forms. They constitute 

 what has passed as Aspidium Boottii. These plants are not constant in character, 

 but seem to represent various combinations of the characters of the two parents. 



6. Polystichum Roth 



1. P. acrostichoides (Michx.) Schott. {Aspidium acrostichoides of authors.) 

 Christmas Fern. 



Dry rocky, sandy, or gravelly woodlands, in neutral, slightly calcereous to acid, 

 soils ; common, especially in ravines, and very generally distributed. June 10-July. 



N. S. to Ont. and Wis., southw. to Ga., Fla. (?), and Tex., including the Coastal 

 Plain. 



A form with the pinnae incised or pinnatifid and the fertile part usually less con- 

 tracted, is forma incisum (Gray) Gilbert. 



7. Dennstaedtia Bernh. 



1. D. punctilobula (Michx.) Moore. (Dicksonia punctilobula and D. pilosiuscula of 

 authors.) Hay-scented Fern. 



Dry or damp sterile open woods, hillside pastures, and about swamps, in gravelly, 

 weakly calcareous to more or less acid, soils ; locally very common. July 25-Sept. 15. 



Abundant in the McLean and Freeville region ; rare about Ithaca ; occasional 

 elsewhere, as: n. w. of Spencer station; n. of Caroline Center; Besemer ; Six Mile 

 Creek ; w. of Townley Swamp ; Howland Island ; Botrychium Woods, Spring Lake. 



N. S. to Minn., southw. to Ga. and Mo. ; less frequent on the Coastal Plain, and 

 lacking in the more sandy parts of that region. 



8. Athyrium Roth 

 a. Fronds 1-pinnate. 1. A. angustifolium 



a. Fronds 2-pinnate. 



b. Sori straight; segments slightly crenate. 2. A. acrostichoides 



b. Sori mostly curved, often horseshoe-shaped ; segments incised or sharply serrate. 



3. A. angustum 



1. A. angustifolium (Michx.) Milde. (Asplenium angustifolium Michx.) Spleen- 



wort. 



Rich bottom-land woods, or deep woods on ravine slopes, with much humus, mostly 

 in neutral soils ; infrequent. Aug. 15-Sept. 20. 



Enfield Glen, just below Lucifer Falls; Six Mile Creek, s. side below the Nar- 

 rows (D. in C. U. Herb.!); Taughannock Gorge; Salmon Creek, Genoa; Paine 

 Creek; Big Gully; rich woods near Stark Pond; low woods s. w. of Westbury. 



W. Que. to Wis., southw. to Ga., Ala., Mo., and Kans. A plant of the rich lands 

 of the interior. 



2. A. acrostichoides (Sw.) Diels. (Asplenium acrostichoides Sw., A. thclyptcroidcs 



Michx.) Spleen wort. 



Deep rich woods, in humus over rocky or gravelly subcalcareous or slightly acid 

 soils; infrequent. July 25-Sept. 15. 



N. e. of Spencer Lake; Newfield Glen; Enfield Glen, just below Lucifer Falls; 

 Six Mile Creek, s. side below the Narrows (D. in C. U. Herb.!) ; Salmon Creek; 

 Big Gully. 



N. S. to Minn., southw. to Ga., Ala., and Mo. ; rare on the Coastal Plain. A 

 plant primarily of the Allegheny region. Found also in Asia. 



Sterile fronds, especially when young, often resemble those of Thelypteris nove- 

 boracencis, from which they may be distinguished by the shaggy pubescence and the 

 hard tooth-like projections on the edges of the stipe near the base. 



