660 FILICES. (FERNS.) 



into 3-5 decurrent divisions, those of the fertile frond oblong or linear-oblong, 

 entire or sparingly incised ; of the sterile ovate or obovate, crenate or incised ; 

 veins of the fertile fronds mostly only once forked. (Pteris gracilis, Miclix. 

 Allosorus gracilis, Presl, and former ed. Shaded calcareous rocks, Vermont 

 1 and Northern and Central New York, to Wisconsin- and northward : rare. 

 July. Rootstock very slender, creeping : stipes polished, brownish, darker and 

 sparingly chaffy at the base. 



2. P. atropurptirea, Link. Smooth, except some bristly-chaffy hairs on 

 the midribs and especially on the dark-purple and polished stalk and rhachis, 6'- 

 15' high ; frond coriaceous, pale, once or below twice'pinnate ; the divisions broadly 

 linear or oblong, or the sterile sometimes oval, chiefly entire, somewhat heart- 

 shaped or else truncate at the stalked base ; veins about twice forked. ( Pteris 

 atropurpurea, Z. Allosorus atropurpureus, Kunze, and former ed.) Dry cal- 

 careous rocks : not common, but of wide range. July. Rootstock short and 

 stout : stipes clustered. 



6. ALLOSORUS, Bernhardi, Link. ROCK-BRAKE. 



Fruit-dots roundish or elongated and extending far down on the free forking 

 veins. True involucre or indusium none, the herbaceous margins of the fertile 

 segments at first reflexed and meeting at the midrib, at length opening out flat 

 and exposing the confluent sporangia. Low, with smooth, 2 -3-pinnate fronds, 

 the fertile ones taller than the sterile, and with much narrower divisions. (Name 

 from oAAoS, various, and crcopds 1 , a heap.) 



1. A. acrostichoides, Sprengel. Stipes densely tufted, straw-colored; 

 fronds 2 -3-pinnate (6' -10' high); fertile segments stalked, linear or linear- 

 oblong (3" -5" long), the sporangia in lines extending dOAvn the veins almost 

 to the midrib, confluent when ripe and covering the under surface of the now 

 fully opened segments; sterile fronds on much shorter stipes, with ovate or 

 obovate decurrent and crenately toothed or incised segments. (Cryptogramme 

 acrostichoides, R. Br.) Isle Royale, Lake Superior, thence westward and 

 northward. Very near A. crispus of Eu. 



7. WOODWARDIA, Smith. CHAIN-FERN. (PI. 16.) 



Fruit-dots oblong or linear, arranged in one or more chain-like rows on trans- 

 verse anastomosing veinlets parallel and near to the midrib. Indusium fixed by 

 its outer margin to the fruitful veinlet, free and opening on the side next the 

 midrib. Veins more or less reticulated, free towards the margin of the frond. 

 Large Ferns, with pinnatifid or pinnate fronds. (Named for Thomas J. 

 Woodward, an English botanist.) 



1. ANCHfSTEA, Presl. Sterile and fertile fronds alike: veins forming only one 



row of meshes (areoles). 



1. W. Virginica, Smith. Fronds (2 -3 high) pinnate, with numerous 

 lanceolate pinnatifid pinnae ; segments oblong ; veins forming a row of narrow 

 areoles along the midrib both of the pinnae and of the lobes, the outer veinlets 

 free ; fruit-dots oblong, one to each areole, confluent when ripe. Wet swamps, 

 Maine to Virginia, and southward. July. 



