360 TEEN FA MILT. 



§ 2. Stems annual, not living through the lointer, branched, at least thesterih ones. 



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

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

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



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

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

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

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



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

 woods : fertile stems appea;rihg 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 

 Xcirdnate) 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 pinnatijid frond are properly called segments ; of a pinnate 

 frond, pinnfE ; of a 2-3 -i-fdnnate frond,. pinnules or ultimate segments. The stalk 

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

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

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



I. POLYPODIACBiE, 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 defnite fruit-dots, but the spore-cases in large patches on the ^tnder surface 

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



1. ACEOSTICHUM § CHRYSODIUM. Fronds simple or pinnately branched, 



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

 frond or of its upper divisions. 



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



in lai-ge patches on special portions of the under surface. 



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

 (soi-i) placed on the veins or at the ends of the veins, but without indusium of 

 any kind. 



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

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

 point where several veins meet {anastomose). Stalk articulated to the root- 

 stocl^ and leaving a distinct scar when decayed away. 

 14. PHEGOPTERIS. Agrees with Polypodiura in mostrespects; but has the fruit- 

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

 not articulated to the rhachis. 



4. GYMNOGRAMME § CEKOPTERIS. Fronds compound, covered beneath 

 with white or yellow waxy powder: fruit-dots in long often forking linos 

 on the veins. 



