FERN FAMILY. 487 



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

 consisting of 1-celled spore cases (technically called sporangia) 

 variously grouped in dots, lines, or masses (called sorl or fruit 

 dots) and containing but one kind of minute, 1-celled, powdery, 

 numerous spores, which are discharged when the sporangia 

 finally split open. A large family, most abundant in warm 

 and moist regions. 



\_The divisions of a pinnatifid frond are x>roperly called segments; of 

 a pinnate frond, pinnce ; of a 2-3-i-pinnate frond, pinnules or idtimate 

 segments. Tlie stalk of the frond is a stipe ; its rinitiiiinrtinii through the 

 frond, the rhachis ; its branches, partial or s(<iiitihirij rhur//isi-s. A rha- 

 chis bordered bij the leafj portion becomes a midrib, irju'r/i uuuj he primanj, 

 secondary, etc.) 



I. POLYPODIUM SUBFAMILY. Characterized by stalked 

 spore cases, having a vertical, iacomplete,'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 rndusium). 



§ 1. Xo flefiiiite fruit dots, but the spore cases in large patclies on the under surface of 

 the fertile frond, or entirely covering the under surf ace ; no indusium. 



1. ACROSTICHUM § CHRYSODIUM. Kronds simple or pinnately branched, with retic- 



ulated veins ; spore cases covering the whole under surface of the frond or of its 

 upper divisions. 



2. PLATY('ERIUM. Fronds irreg'ularly forking ; veins reticulated ; spore cases in larffc 



patches on special portions of the under surface. 

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

 (sort) placed on tlie veins or at the ends of tlie reins, but without inditsium of 

 any kind. 



3. POLYPODirN[. Fronds simple or pinnate, rarely twice pinnate ; veins free or retic- 



ulated ; frnit dots round. or roundish, at the ends of the veins, or at the point where 

 several veins meet {anastomose). Stalk articulated to the rootstock, and leaving a 

 distinct scar when decayed away. 

 (15. PHEOOPTERIS may besought here.) 



4. GYMNOGRAMME § CEROPTERIS. Fronds compound, more or less covered beneath 



with white or yellow waxy powder ; fruit dots in long often forkinp- lines on the 

 veins. 



5. NOTHOL.EN.\. Fronds once or twice pinnate, woolly, scaly or powdery beneath; 



fruit dots at the ends of the veins, forming a line next the )narfjin of the divisions. 

 § 3. Spore cases on the back along the margin of the frond, provid^;d ivith an involucre 

 formed of its reflexed and more or less altered margin. 



6. ADIANTUM. Fruit dots at the ends of the veins, borne on the inner side of a relieved 



portion of the mariri;!. Stalk dark and polished, sometimes eliatTy-bristly. Pinnules 

 always separate, distinctly stalked or almost sessile, but ni'ver decurrent on the 

 rhachis. 



7. PTERI3. Spore cases on a transverse, vein-like receptacle within the margin, which 



connects the ends of the veins, and is covered by the reflexed thin margin. Stal!-- 

 light-colored (except in § Doryopteris). Pinnules or ultimate segments adnata to 

 the rhachis, often decurrent. 



