POL YPODIA CE^. 9 1 



usually in 2 — 6 opposite sessile pairs, the sterile ones considera- 

 bly the broadest and spinulose-serrate, the lower pairs often 

 cleft nearly to the base, into two or three linear pinnules ; veins 

 fine, parallel, simple or once forked ; indusium pale. Florida. 

 ' 3. P. serrulata Linn. f. Stipes 6' — 9' long, naked, pale 

 or brownish ; fronds 9' — 18' long, 6' — 9' broad, ovate, bipinna- 

 tifid, the main rachis margined with a wing which is i" — 2" 

 broad at the top and grows narrower downwards ; pinnae in six 

 or more distinct opposite pairs, upper ones simple, the lower 

 ones with several long linear pinnules on each side, the edge of 

 the barren ones spinulose-serrate ; veins simple or once forked. 

 Alabama {Mohr), Macon, Georgia, {Farnell). An escape from 

 cultivation. 



XII. PTERIDIUM Scopoll. 



Sori marginal, linear, continuous, occupying a slender fili- 

 fc^rm receptacle which connects the tips of the free veins. In- 

 dusium double ; the outer formed of the incurved membranous 

 margin of the frond, as in Pteris, and the inner attached within 

 the receptacle and extending beneath the young sporangia. 

 Veins free. Name from Gr. icrepii, a fern. Two or more species. 



■CL I. p. aquilinum (L.) Kuhn. Rootstock stout, wide-creeping, 

 subterranean ; stipes 1° — 2° high, erect, stramineous or brownish; 

 fronds 2° — 4° long, 1° — 3° wide, ternate, the three branches each 

 bipinnate ; upper pinnules undivided, the lower more or less 

 pinnatifid. North America everywhere. 



Var. caudatum (L.) Kuhn. Pinnules sometimes linear and 

 entire, or with less crowded segments than the type and the 

 terminal lobe linear and entire. (P. caudaia L.) Florida and 

 Texas. Probably a distinct species. 



' Var. pubescens Underw. Fronds silky-pubescent, to- 

 mentose, especially on the under surface; otherwise as in the 

 typical form. (P. aquilina, var. lanuginosa of former editions, 

 not P. lanuginosa Bory.) Utah, California, and northward. 



XIII. CHEILANTHES Swz. Lip-fern. 



Sori terminal or nearly so on the veins, at first small and 



roundish, afterwards more or less confluent. Indusium formed 



of the reflexed margin of the frond, roundish and distinct, or 



more or less confluent. Veins free. Name from Gr. ;t;etA.oS, a 



