FILICES. 545 



clusters of thecse. Certain cellular papillas on the margin or upper 

 surface of the fronds have been considered by some as antheridia, 

 each of the cells containing a spiral fibre. Link and others state, that 

 among the young thecas (pistilidia), filamentous bodies occur, which 

 are equivalent to stamens. Ferns are elegant leafy plants, occurring 

 chiefly in moist insular climates, and abounding in the tropical islands. 

 In mild and warm climates they occur in the form of large Tree- 

 ferns, fifty to sixty feet high, which give a character to the landscape. 

 The theca of ferns has been looked upon as a modified leaf, having 

 the same gyrate or circinate development as the frond. Leaves have 

 occasionally been produced in place of thecas. Ferns having the thecae 

 on the back of the frond, and furnished with an elastic ring or band, 

 are called dorsiferous and annulate; while those having no thecal ring 

 are exannulate. 



1109. The order has been divided into several suborders: 



1 . Polypodies, thecoe on the back of the frond, pedicellate or sessile, distinct, annu- 

 late, ring vertical, usually incomplete, bursting irregularly and transversely. 



'2. Hymenophyllea?, thecae marginal or dorsal, nearly sessile, distinct, annulate, 

 ring horizontal, complete, occasionally oblique, bursting lengthwise. 



3. Osmundete, theciE dorsal, or forming a separate stalked mass (an altered 



frond), distinct, with a terminal or dorsal ring more or less incomplete, 

 bursting lengthwise. 



4. Ophioglosseas, thecas collected into a spike, formed at the edges of an altered 



frond, distinct, exannulate, two-valved 



5. Danasese, thecaj united in masses, exannulate, opening irregularly by a central 



cleft. 



The generic characters of Ferns are founded on the position and direc- 

 tion, covered or uncovered nature of the sori, as well as on the venation. 

 Lindley notices 192 genera in his Filical Alliance, including upwards 

 of 2000 species. Kunze estimates the species at 3000. There are 

 not above 700 species cultivated in Europe. In 1846 there were 387 

 species grown in the Royal Garden at Kew. Examples Polypodium, 

 Aspidium, Lastrea, Grammitis, Adiantum, Pteris, DavaUia, Woodsia, 

 Cyathea; Hymenophyllum, Trichomanes, Aneimia, Lygodium; Os- 

 munda; Ophioglossum, Botrychium; Danasa. 



1110. Few of the Ferns are used medicinally. They are in general 

 demulcent and astringent. Some yield food. The rhizome of Lastred 

 Filix-mas, Male-shield fern, has been used as a vermifuge, especially in 

 cases of tape-worm. It contains starch, gum, saccharine matter, tan- 

 nin, green fixed oil, and resin. Its properties are ascribed to the fixed 

 oil. The rhizome has been used for tanning, and its ashes contain much 

 carbonate of potash. The syrup called capillaire, and certain pectoral 

 mixtures are prepared from Adiantum pedatum and A. Capillus Veneris 

 The rhizome of Pteris esculenia is used as food in Australia, and that of 

 Marattia alata in the Sandwich islands. Many other species of Ferns 

 are esculent. The stems and leaf-stalks of Ferns are often covered 



2N 



