FILICE8. 



377 



furnislied with a usually incomplete, nearly vertical, or rather oblique 

 ring. Receptacle prominent, barrel-Bliaped (Fig. 265). Tree-ferns. 

 Genera three (Cyathea, Hemittlia, and Alsophila) ; species 150, mostly 

 tropical and subtropical. 



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

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



Fig. 263. 



Fio. 264. 



Fig. 265. 



Fig. 263. — Portion of a leaf of Gleich&nia^ with a sorus, a; 6, a sporangium. — Af- 

 ter Hoolce]-. 



Fig. 264.— Portion of a leaf of Trichomanen^ a, with iive sori ; 6, a sporangium. — 

 After Hooker. 



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

 ceptacle ; 6, a sporangium. — After Hooker. 



inent (Figs. 3576 to 361). Genera fifty (Acrostichum, Polypodium, 

 Adiantum, Pteris, AspUnium, SeolopewJrium, Aspidnm, Cysiopteris, 

 etc.) ; species 3000, widely distributed throughout the world. 



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

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

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

 north and south temperate re- 

 gions. 



6. SchizmaceCB. — Sporan- 

 gia sessile, splitting vertical- 

 ly, crowned by a complete 

 small annular horizontal ring 

 <Fig. 367). Genera five 

 {ScMzma, Anemia, Lygodiwm, 

 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 meduUaris) 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 



Fig. 266. 

 Fig. 366. —Two 



Fib. 267. 

 sporangia of Osmunda; 



with the rudimentary ring peen in front view ; 

 J, with the ring seen in profile.— After Hooker. 

 Fig. 267.— Lower portion of a fertile i inna. a, 

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



