FILIGES. 



377 



furnislied witli a usually incomplete, nearly vertical, oi' rtttlier oblique 

 ring. Receptacle prominent, barrel-shaped {Vicr, 365). Tree-ferns. 

 Genera three [Cyathea, Semitelia, and AUophila) ; species 150, mostly 

 tropical and subtrnpical. 



4. Polypodiacem. — Sporangia stalked, splitting transversely, fur- 

 nished with a usually incomplete vertical ring. Receptacle not prom- 



FlG. 263. 



Via. 264. 



FiQ. 265. 



Pig. 26.S. — Portion of a leaf of Oleicli&rUa, with a £orus, a ; 5, a sporangium. — Af- 

 ter Hooker. 



Fig. 264. — Portion of a leaf of Trichomanen^ a, with five gori ; 6, a sporangium. — 

 After Hooker. 



Fig. 265. — Vertical section of a sorus, a, of Alsophila^ showing the cylindrical re- 

 ceptacle ; b, a sporangium. — ^After Hooker. 



inent (Figs. 2576 to 261). Genera fifty (Aerostielium, Polypodium, 

 Adiantum, Pteris, Asplenium, Scolopendrium, Aspidium, Oystopteris, 

 etc.); species 2000, widely distributed throughout the world. 



5. Osmundacem. — Sporangia stalked, splitting vertically, furnished 

 with only a faint horizontal bar, instead of a ring (Fig. 266). Genera 

 two {Osmunda and Todc a) ; species ten to twelve, widely distributed in 

 north and south temperate re- 

 gions. 



6. Sch 'zceacem. — Sporan- 

 gia sessile, splitting vertical- 

 ly, crowned by a complete 

 small annular horizontal ring 

 (Fig. 267). Genera five 

 (Sehizma, Anemia, Lygodium, 

 etc.); species sixty, mostly 

 natives of the warm regions 

 of America and Asia. 



Economically the true Ferns are of comparatively little value. The 

 pulpy interior of the stem of a tree-fern (Cyathea medidlaris) growing 

 in the Pacific islands furnishes an important article of food to the 

 natives. In Australia the underground stems of Pteris aquilina 

 supply an indifferent food. A few species are of doubtful value as 

 astringent medicines. The long woolly hairs of certain species ot 



m 



Fig. 266. Fig. 267. 



Fig, 266. —Two sporangia I'f Osmunda; a. 

 with the rudimentary ring pcen in front view ; 

 b, with the ring seen in iirciflle.— After Hooker. 



Fig. 267.— Lower port,ion of a fertile iiinna, a, 

 of Schiscea ; b, a sporangium. — After Hooker. 



