BOTRYCHIUM.] FILICES. 521 



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

 small globose coriaceous capsules which burst transversely. Spores minute. 

 DISTKIB. Temp, and trop. regions ; species 6. ETYM. jSorpvs, from 

 the clustered sori. 



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



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

 lands ; Ireland ; frt. June-Aug. Rnotstock 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. DISTKIB. 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'CE/B. 



RootstocJc 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 (claters), which 

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

 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 steins 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. 

 Roadsides, banks and fields, N. to Shetland; ascends to 2,00) ft. in N. 

 England ; Ireland ; Channel Islands ; frt. April. Barren stems 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. DlSTKEB. Europe (Arctic) N, Africa, N, Asia, Himalaya, 

 N. America. 



