POLYPODIACEAE 15 
sterile leaf-blades. Sori round, borne on the back of the veins. Indusium very thin and 
membranous, hemispheric or hood-shaped, fixed at the inferior side of the sorus. Sporo- 
phylls unrolling at maturity, allowing the spores to escape, and remaining long after the 
sterile leaves have been killed by frost. Veins forming small areolae. 
1. Onoclea sensibilis L. Leaves 3-13 dm. high ; blades triangular, deeply pinnati- 
fid ; segments lanceolate-oblong, entire, undulate, or the lower pairs sinuate-pinnatifid : 
sporophylls 3-7 dm. high, persistent over winter, much contracted and with short pin- 
nules rolled up into berry-like closed involucres forming a narrow panicle. 
In moist soil, Newfoundland to Ontario and Minnesota, south to the Gulf of Mexico.—Various 
forms intermediate between sporophylls and foliage leaves occur. Summer and fall. SENSITIVE FERN. 
21. TECTARIA Cav. 
Plants with horizontal rootstocks. Sori round, borne on the back of the leaflets or 
leaf-segments. Indusium peltate, opening all around the margin. Veins everywhere 
anastomosing, forming copious areolae, with free included veinlets. 
1. Tectaria trifoliàta (L.) Cav. Leaves tufted, 6-7.5 dm. tall; petioles brownish, 
scaly at the base ; leaf-blades 3-4.5 dm. long, each with a large ovate-acuminate terminal 
leaflet narrowed or forked at the base, and 1 or 2 lateral leaflets, the lowest mostly forked : 
primary veins distinct to the margin: areolae fine: sori in 2 rows near the main veins : 
indusia orbicular, peltate. [Aspidium trifoliatum (L.) Sw. ] 
In sandy soil, peninsular Florida and Texas. Also in tropical America. 
22. POLYSTICHUM Roth. 
Coarse plants, often with chaffy foliage. Leaves tufted: petioles not jointed to the 
rootstock ; blades 1-2-pinnate, the sterile and fertile similar. Sori usually borne on the 
backs of the veins. Indusium superior, centrally peltate, orbicular. Veins free. 
1. Polystichum acrostichoides (Michx.) Schott. Rootstocks stout. Leaves ever- 
green, 2.5-8 dm. tall; petioles densely chaffy ; blades lanceolate, those of the fertile ones 
contracted near the top, 1.5-6 dm. long, 1-pinnate ; leaflets somewhat leathery, linear- 
lanceolate, 2.5-7 cm. long, falcate, half-hastate at the base, with appressed bristly teeth, 
bearing the large contiguous sori, which soon cover the whole lower surface near the mid- 
dle. [-Aspidium acrostichoides ( Michx. ) Sw.] 
In woods and on rocky banks, Nova Scotia to Wisconsin, south to Forida and Mississippi. CHRIST- 
MAS FERN, 
23. DRYOPTERIS Adans. 
Terrestial plants with erect or horizontal rootstocks. Leaves tufted, the sterile and 
fertile similar: blades 2-3-pinnate or -pinnatifid : petioles not jointed to the rootstocks. 
Indusium flattish, cordate-reniform, superior, fixed by the sinus. Veins free or basal 
veinlets united. Often known as SHIELD-FERNS. 
Leaf-blades thin-membranous: veins simple or 1-forked. 
Lower leaf-segments reduced to mere lobes. 
Rootstock stout, erect, forming a short caudex. 1. D. contermina. 
Rootstock slender, horizontal. 2. D. Noveboracensis. 
Lower leaf-segments little smaller than the central. i à 
Veins forked : leaf-blades dark green, relatively firm. 3. D. Thelypteris. 
Veins simple : leaf-blades pale green, thin-flaccid. 4. D. patens. 
Leaf-blades firm or leathery : veins freely forking. 
Leaf-blades 2-3-pinnatifid : veins always free. ; 
Leaf-blades 2-pinnatifid or 2-pinnate: divisions not spinulose. 
Indusia large, thinnisn, flat: sori midway to the margins. 
Leaflets or segments broadest at the base. 
Fertile and sterile leaflets alike, deltoid or triangular. 5. D. cristata. 
Fertile leaflets narrowly lanceolate, unlike the sterile ones. 6. D. Floridana. 
Leaflets or segments broadest at the middle. : 7. D. Goldieana. 
Indusia convex, without marginal glands: sori near the margin. 8. D. marginalis. 
Leaf-blades 2-pinnate or 3-pinnatifid : divisions spinulose-tipped. P. ys INN 
. unita. 
Leaf-blades pinnate : contiguous veinlets united. 
1. Dryopteris contérmina ( Willd.) Kuntze. Rootstocks erect, often 3 dm. above the 
surface of the ground. Leaves in a crown ; petioles narrowly wing-margined at the base ; 
blades 3-12 dm. long, lanceolate, cordate-acuminate at the apex, rather rigid, narrowed at 
the base ; leaflets sessile, narrowly lanceolate from a broader base, acuminate, deeply pinnat- 
ifid ; segments obtuse, obliquely and slightly falcate, copiously resinous-dotted beneath : 
sori near the margins : indusia minute, reniform, glandular and pilose, evanescent. 
In swamps near Fort Meade, Florida.—The form within our range is known as D. contermina 
strigósa (Fée) Underw., to which the above description mainly applies. 
