360 FERN FAMILT. 



§ 2. Stems annual, not living through the tmnter, branched, at least the sterile ones. 



B. limbsum. Muddy edges of streams, rather common : stems all alike, 

 2° - 3° high, with many furrows, fhiiting in summer, and afterwards sending 

 out a few upright branches ; sheaths with 15-20 dark-colored acute teeth. 



E. arv6nse. Common Horsk-tail. Moist sandy places, common N. : 

 fertile stems unbranched, with very conspicuous sheaths, 4' - 8' high, appearing 

 in earliest spring and soon withering; sterile stems 8' -20' high, producing 

 many whorls of rather rigid slender and mostly simple 4-angled branches. 



E. sylv&,tieum, Woodland H. Common N., along the edges of moist 

 woods : fertile stems appearing in early spring, but lasting all summer, both 

 these and the sterile ones producing many whorls of spreading or gracefully 

 decurved compound softish 3 - 5-furrowed branches and branchlets ; sheaths of 

 the main stem loose, 8 - 14-toothed. 



132. PILICES, FERN FAMILY. 



Flowerless plants with creeping or ascending rootstocks, or even 

 erect trunks, bearing distinct leaves (fronds), which are rolled up 

 (circmate) in the bud (except in one group), and bear commonly on 

 the under surface or on the edges the simple fructification, consist- 

 ing of 1 -celled spore-cases (technically called sporangia) variously 

 grouped in dots, lines, or masses, and containing but one kind of 

 minute, 1-celled, powdery, numerous spores. A large family, most 

 abundant in warm and moist regions, consisting of 8 suborders, 6 of 

 which are represented with us. 



[The divisions of a pinnatifid frond are properly called segments ; of a pinnate 

 frond, pinnoe ; of a 2 - 3 - 4-pinnate frond, pinnules or ultimate segments. The stalk 

 of the frond is a stipe ; its coTUinuatiun through the frond, the rhachis ; its branches, 

 partial or secondary rhachises. A rhachis bordered by the leafy portion becomes a 

 midrib, which may be primary, secondary, ^c] 



I. POLYPODIACEJE, or TRUE FERNS: characterized by 

 stalked spore-cases, having a vertical, incomplete, many-jointed, 

 elastic ring, which straightens at maturity, breaking open the spore- 

 case transversely, and so discharging the spores. Spore-cases rarely 

 if ever on very narrow thread-like branches ; the fruit-dots often 

 covered by a scale-like involucre (the indusium). 



§ 1. No definite fndt-dots, but the spore-cases in large patches on the under surface 

 of the fertile frond, or entirely covering the under surface: no indusium. 



1. ACROSTICHUM § CHRYSODItJM. Fronds simple or piunately branched, 



with reticulated veins : spore-cases covering the whole under surface of the 

 frond or of its upper divisions. 



2. PLATYCERIUM. Fronds irregularly forking; veins reticulated: spore-cases 



in large patches on special portions of the under surface. 



§ 2. Spore-cases on the bach of the frond, sometimes near the margin, in dots or lines 

 (sort) placed on the veins or a^ the ends of the veins, but without indusium of 

 any hind. 



3. POLYPODIUM. Fronds simple or pinnate, rarely twice pinnate; veins free 



or reticulated ; fruit-dots round or roundish, at the ends of the veins, or at the 

 point where several veins meet (anastmnose). Stalk articulated to the root- 

 stock, and leaving a distinct scar when decayed away. 

 14. PHEGOPTERIS. Agrees with Polypodium in most respects ; but has the finiit- 

 dots smaller, and commonly on the veins, not at their ends, and the stalk is 

 not articulated to the rhachis. 



4. GYMNOGRAMME § CEROPTERIS. Fronds compound, covered beneath 



with white or yellow waxy powder: fruit>dots in long often forking lines 

 on the veins. 



