riLiCES. 63* 



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 thecse. The prothallus of 

 Pteris serrulata is said to produce occasionally fronds without the 

 agency of archegonia. This case is similar to the formation of adven- 

 titious buds or leaves. Ferns having the thecse 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. 

 The order has been divided into several sub-orders : — 



1. Gleicheniese, Gleichenia tribe. — Son dorsal, sporangia (thecse or capsules), 



opening vertically, surrounded ty a broad transverse complete ring (annu- 

 1ns), no indusion (involucre), vernation cii'cinate. 



2. Polypodies, Polypody tribe. — Sori dorsal, sporangia pedicellate or sessile, dis- 



tinct, annulate, ring vertical, usually iacomplete, bursting irregularly and 

 transversely, involucre marginal, dorsal, or 0, vernation circinate. 



3. Hymenophylleae, Filmy Fern tribe. — Sori marginal or dorsal, involucre 



2-valved, sporangia nearly sessile, distinct, annulate, ring horizontal, complete, 

 occasionally oblique, bursting lengthwise, vernation circinate. 



4. Osmnndeae, Eoyal or Flowering Fern tribe.' — Sporangia 2-valved, dorsal, or 



forming a separate stalked mass (an altered frond), distinct, "with a short 

 horizontal and more or less Incomplete ring, opening across the apex, no in- 

 volucre, vernation circinate. 



5. Schizsese, Schizaea tribe. — Sporangia 2-valved, opening along the side, crowned 



by a complete opercular ring, vernation circinate. 



6. MarattieiE, Marattia tribe. — Sporangia united in mass (synangia), exannulate, 



opening irregularly by a cleft on one side or by a pore at the apex, vernation 

 circinate. 



7. OpMoglosseae, Adder's-tongue tribe. — Sporangia collected into a spike, formed 



at the base of an altered frond, exannulate, 2-valved, vernation straight. 

 They have a pale underground prothallus, bearing antheridia and archegonia. 



The generic characters of Ferns are founded on the position and 

 direction, covered or uncovered nature of the sori, as well as on the 

 venation. There are 240 genera, including upwards of 2600 species. 

 Examples — Gleichenia ; Polypodium, Aspidium, Lastrea, Asplenium, 

 Adiantum, Pteris, Davallia, Woodsia, Cyathea ; Hymenophyllum, 

 Trichomanes ; Schizsea, Aneimia, Lygodium ; Osmunda ; Dansea, 

 Marattia, Angiopteris ; Ophioglossum, Botrychium. 



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

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

 (Aspidium) Filix-mas, Male shield-fern, has been used as a vermifuge, 

 especially in cases of tapeworm. It contains starch, gum, saccharine 

 matter, tannin, green fixed oil, and lesin. Its properties are ascribed 

 to the fixed oil. The rhizome has been used for tanning, and its 

 ashes contain much carbonate of potash. Cyathea medullaris, Ponga 

 of New Zealand, furnishes a gum used as a vermifuge. The syrup called 

 CapiUaire, and certain pectoral mixtures, are prepared from Adiantum 



