Botrychium.] FILICES. 521 



fertile branched receptacle, covered on the surface facing the blade with 

 small globose coriaceous capsules which burst transversely. Spores minute. 

 — Distrib. Temp, and trop. regions ; species 6. — Etym. f$6rpvs, from 

 the clustered sori. 



B. Imna'ria, Sw. ; blade about the middle of the frond pinnate. 



Pastures and grassy banks, N. to Shetland ; ascends to 2,700 ft. in the High- 

 lauds ; Ireland ; frt. June-Aug. — Rootstock tuberous, enclosing at its top the 

 bud of the next year's frond. Frond 3-6 in., stout, terete, fleshy, glabrous ; 

 blade §-2 in., oblong ; pinnae ^-circular or lunate, close-set, entire crenate 

 toothed or subpiunatifid. Receptacle |-3 in., erect, segments narrow, in- 

 curved. Capsules sub-2-seriate on the segments. — Disthib. Europe 

 (Arctic), N. and S. temp, and cold regions. 



A form with the frond deltoid, pinnules 3-4 pairs incised or pinnatifid, lobes 

 linear or cuneate 1-nerved, found on the sands of Barry, has been doubtfully 

 referred to B. rutaceum, Sw. 



Order XCL— EQUISETA'CEiE. 



Bootstock creeping. Stem erect, terete, jointed, grooved, hollow except 

 at the joints, and with air-cells in their walls under the grooves, joints 

 terminating in toothed sheaths ; teeth corresponding with the ridges ; 

 branches if present arising from the sheath-bases, solid. Capsules 6-9, 

 1-celled, on the under surface of the peltate scales of a terminal cone. 

 Spores of one kind, attached to 4 clubbed elastic threads (elaters), which 

 are coiled round the spore when moist, and uncoil when dry. — Distrib. 

 Chiefly temp. N. regions, a few are sub-trop. ; none are high southern ; 

 genus 1 ; species 25. — Affinities. None direct. — Properties. The 

 cuticle abounds in siliceous cells ; whence the stems of some are used 

 for polishing. 



Germination and impregnation as in Filices ; but the prothallus is usually 

 (functionally) 1- sexual. 



1. EQUISE'TUM, L. Horse-tail, Paddock-pipes. 



Characters of the Order. — Etym. equus, seta, horse bristle. 



* Fruiting stems simple or rarely branched, succulent ; barren appearing 

 later, branched ; branches simple. 



1. E. arven'se, L. ; barren stems 6-19-grooved, branches spreading, 

 sheaths of fruiting stems distant loose with teeth ribbed to the tip. 

 Eoadsides, banks and fields, N. to Shetland ; ascends to 2,000 ft. in N. 

 England ; Ireland ; Channel Islands ; frt. April. — Barren ste?ns erect or de- 

 cumbent, slightly scabrid, usually ending in a long naked point ; branches 

 crowded, 4-gonous ; fertile stems (rarely with branches) stouter, shorter ; 

 sheaths scarious. — Distrib. Europe (Arctic) N. Africa, N. Asia, Himalaya, 

 N. America. 



