This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Small terrestrial plants, with small, erect, fleshy, often tuberous, rootstocks bearing fibrous naked roots and 1-6 slender, erect leaves, these consisting usually of a short, cylindric common stalk, bearing at its summit a simple entire lanceolate to reniform sessile or short-stalked sterile blade with freely anastomosing veins and usually a single simple long-stalked spike, the sporophyl, formed of 2 rows of large coalescent sporanges; spores copious, sulphur yellow. Bud for the following season borne at the apex of the rootstock, exposed, distinct and free from the leaf of the present season. [Name from the Greek, signifying the tongue of a snake, in allusion to the form of the narrow spike.]
Leaves usually solitary; sterile blade obtuse or acutish, never apiculate.
Leaves often in pairs; sterile blade acutish or apiculate.
Sterile blade elliptic, rarely ovate, apiculate; areoles broad.
Sterile blade lanceolate, acutish, somewhat apiculate; areoles narrow.
*Text (except Equisetaceae and Isoetaceae) revised by William R. Maxon.
Ophioglossum vulgatum L. Sp. PI. 1062. 1753.
Rootstock short, oblique or erect; leaves usually solitary, 3-16' long, the common stalk usually one-half or more above ground and constituting one-third to two-thirds the length of the plant; sterile blade lanceolate, oblanceolate or spatulate, elliptical, oblong or ovate, 1-5' long, l'-2' broad, sessile, obtuse or acutish, the middle areoles long and narrow, the outer ones shorter and hexagonal, with included veins; sporophyl 3/4-2' long, borne on a stalk 4'-10' long, solitary, apiculate from the prolongation of the axis.
In moist meadows and boggy thickets, Prince Edward Island to Ontario, south to Florida. Also in Europe and Asia. The genus is also called Adder's-fern or -spear. Snake's-tongue. Serpent's-tongue. May-Aug.
Ophioglossum Engelmanni Prantl, Ber. Deuts. Bot. Ges. 1: 351. 1883.
Rootstock cylindric, with long brown roots; leaves commonly 2-5, mostly fertile, 3'-9' long, the common stalk often mostly below the ground and usually sheathed by the more or less persistent bases of old leaves; sterile blade elliptic or rarely ovate, 1' - 3 1/2' long, 1/2'-2' broad, sessile, usually acute, apiculate, with wide oblique areoles containing numerous anastomosing or free veins; sporophyl 6"-12" long borne on a stalk 1'-4' long, apiculate; sporanges 12-27 pairs.
In damp, sterile places or on rocks in cedar woods, mainly in the Central States, from Indiana and Virginia to Louisiana, Texas and Arizona. April-Oct.
Rootstock slightly thickened, with numerous fleshy, spreading (sometimes proliferous?) roots; leaves slender but rigidly erect, single or often in pairs, mostly fertile, 2-7' long, the common stalk one-half its length below ground and constituting one-third or less the length of the plant; sterile blade lanceolate, with a long tapering base, or somewhat elliptic, 1'-2' long, 3"-6" broad, acutish or somewhat apiculate, with long, narrow areoles with a few indistinct included veinlets, the outer areoles shorter; sporophyl 6"-13" long, borne on a slender stalk 2'-3 1/2' long, apiculate; sporanges 12-26 pairs.
Gregarious in a colony of many plants in sandy ground under trees at Holly Beach, New Jersey, the type locality. Also in New York and New Hampshire. July.