5 

 2. PTERIS L. Brake ob Bracken. 



Sporangia in a continuous line, marginal; indusium a thin 

 membrane formed from the reflexed margin ; fronds about 3 — 

 pinnate ; midrib of the pinnules central. 



P. AQuiLiNA L. Stipe stout, light colored, 3 — divided at the 

 summit; fi'ond broad, 2—3 feet, twice pinnate; pinnae lanceo- 

 late, long ; pinnules oblong, obtuse, alternate, entire or the low- 

 er frequently lobed or pinnatifid. August — September, Com- 

 mon in all the eastern counties, scarce westward. Prefers 

 shaded upland woods. 



3. ADIANTUM L. Maidenhair. 



Fruit dots oblong, marginal ; indusium formed from the re- 

 flexed mnrgin ; midrib marginal, opposite the sori ; stipe slen- 

 der, shining, black. 



A. PEDATUM L. Frond 8—16 inches high, forked at the 

 summit of the stipe ; branches recurved, bearing from above 

 several slt-nder, diverging, pinnate divisions ; pinnules numer- 

 ous, short stalked, alternnte, oblique, triangular oblong, lower 

 margin entire bearing the obscure midrib from which spring the 

 veins ; opposite margin cleft. July — August. Rich woods. 

 Iowa's commonest fern. Stnte wide • 



4. PELLAEA LINK. 



Sporangia marginal, (resembliug Pteris) composed of conflu- 

 ent elongated or roundish clusters ; indusium broad, membran- 

 aceous, continuous, formed from a modified reflexed margin. 

 Ferns with small 2 — 3 pinnate fonds and dusky stipes. 



P. ATROPURPUREA LiNK. Stipes clustered from a short 

 stout rootstock, dark purple, shining, scarcely with haiiy bris- 

 tles ; fronds pale coriaceous, once or the lower portion twice 

 pinnate; pinnae oblong, truncate at the base; veins twice forked. 

 Low ferns, 4—8 inches high, with a dense tuft of purple chaffy 

 bristles at the base around the cluster of stipes. Grows from 

 the cracks in calcarious clifts. Common locally throughout the 

 limestone regions of the eastern and c&htral parts of the state. 



