HORSETAIL FAMILY 1053 



broad: teeth lance-linear, sharply 3-angled, persistent or coherent by their tips 

 and torn off; cone 1-L5 cm. long, about 5 mm. thick, sharply apiculate. E. 

 robustum affine Engehn. E. hyemales Am. auth., not L. N.S. — N.Y. — Ariz. — 

 Sask. Plain — Submont. Je-Au. 



9. E. intermedium (A. A. Eaton) Rydb. Stems 3-12 dm. high, 5-8 mm. 

 thick, 20-30-angled; ridges rough, with 2 rows of tubercles; sheath longer than 

 broad, green, except a narrow black and white border, sometimes with a dark 

 Ijand beneath; teeth thin, browm, hyaline-margined, deciduous or persistent; 

 cones sessile, about 1 cm. long and 5 mm. thick, apiculate. E. laevigatum Milde, 

 not A. Br. Moist sandy soil: Mich. — Mo. — Calif.— Wash. Plain — Submont. 



10. E. laevigatum A. Br. Stems 1-10 dm. high, 4-6 mm. thick, simple or 

 with erect branches, 20-30-groo ved ; sheaths widened upwards, green, with a 

 black limb; teeth mostly deciduous, with black triangular bases; cones sessile or 

 nearly so, 1-1.5 cm. long, about 5 mm. thick, rather bluntly apiculate. Alluvial 

 soil: Ohio— Tex.— Cahf.— B.C. Plain— Mont. Je-Au. 



11. E. variegatum Schleich. Stems 1.5-3 dm. high, 2-4 mm. thick, 5-10- 

 grooved, tufted; central cavity one-third the diameter; sheaths loose, green below, 

 with a dark ring above; teeth black, with broad white border, persistent, with a 

 filiform deciduous tip; cones short-peduncled or sessile, 8-10 mm. long, about 

 3 mm. thick. Wet grounds: Lab. — N.Y. — Colo. — Alaska. Plain— Mont. 



12. E. scirpoides Michx. Stems tufted, fihform, less than 1.5 dm. high, 

 1-2 mm. thick, flexuose-curving; sheaths short, with 3 subulate, persistent teeth; 

 cones 3-5 mm. long, 2 mm. thick. Damp places: Lab. — Pa. — Mont. — Wash. — 

 B.C.; Eurasia. Submont. — Mont. 



Family 6. ISOETACEAE. Quillwort Family. 



Small water or bog plants, with a corm-like short stem and numerous 

 crowded subulate or nearly filiform leaves. Spores of two kinds, smaller 

 microspores (male) and larger macrospores (female), in axillary sporangia 

 covered by the enlarged bases of the leaves, the macrospores spherical, with 

 an ecjuitorial ring-like ridge and three other ridges meeting at the apex, the 

 micrcspores obliquely oblong, triangular in cross-section. 



1. ISOETES. Quillwort. 



Characters of the family. 



Submerged species; leaves without peripheral bast-bundles. 



Stomata absent; macrospores marked with confluent crests, more or less honey- 

 combed. 1- ^- occidentalis. 

 Stomata pr&sent; macrospores spinulose or tubercled. 



Macro-spores spinulose. 2. I. Braunn. 



Macrospores with low tiibercles. 3. I. Bolanden. 



Amphibious or terrestrial species; leaves with peripheral bast-bundles and stomata. 

 Macrospores, with low blunt isolated or confluent crests; peripheral bast-bimdles 4. 



4. /. Howcllii. 

 Macrospores, with numerous minute tubercles or almost smooth; peripheral bast- 

 bundles 3. 5- I- Nuttallii. 



1. I. occidentalis Renders. Leaves rigid, spreading, quadrangular, dark 

 green, 5-20 cm. long; ligule narrowly triangular; velum covering about one-third 

 of the sporangium; macrospores about 0.4 mm., finely crested, with simple or 

 confluent crests; microspores papillose to echinulate. /. lacustris paupercula 

 Engelm., a depauperate form. In water: Ore. — Wyo. — Colo. — Calif. Plain — 

 Mont. Jl-0. 



2. I. Braunii Durieu. Leaves erect or spreading, green or reddish green, 

 tapering, 7-20 cm. long; velum covering one-half to three-fourths of the spotted 

 sporangia; macrospores 0.4-0.5 mm., with broad retuse spinules; microspores 

 smooth. I. echinospora Braunii Engehn. In water: Greenl. — N.J. — Calif. — 

 B.C. 



