MARSILIA FAMILY 283 



Family 3. MARSILIACEAE. IMarsilia Family. 

 1. MARSILEA L. 



Sporocarps with two distinct acute teeth separated by a rounded sinus, the upper tooth 

 the longer, straight or ciu-ved. 1. M. vestita. 



Sporocarps with the lower tooth short and blunt, the upper a mere rounded papilla or 

 wanting. 2. M. oligospora. 



Family 4. SALVINIACEAE. Salvinia F.imily. 

 1. AZOLLA Lam. l. A. caroliniana^ 



Family 5. EQUISETACEAE. Horsetail Family. 



1. EQUISETUM. Horsetail. 



Stem annual; spike rounded at the top; stomata scattered in the grooves of the stem. 

 Stems of two kinds, the fertile ones succulent, appearing earUer than the sterile ones. 

 Fertile stems simple, soon withering, branchless. 1. E. arvense. 



Fertile stems, when older, producing branches, only the naked ape.x withering. 

 Branches compound; ridges with 2 rows of hooked spinules. 



2. E. sylvaticum. 

 Branches simple; ridges with 3 rows of broad spinules. 3. E. pratense. 



Stems of one kind; branches simple or none. 



Teeth of the sheatlis persistent ; plant usually branched, at least in age. 



Sheaths loose; teeth grooved, black with white margins; central cavity one- 



si.xth of the diameter of the stem. 4. E. palustre. 



Slieath close; central cavity one-half of the diameter of the stem or more. 

 Sheaths 7-8 mm. long; stem stout, sparingly branched. .5. E. fluviatile. 

 Sheaths less than 5 mm. long; stem slender, much branched. (Autumnal 

 forms of) 1. E. arvense. 



Teeth of the sheaths deciduous; plant unbranched or nearly so. 



6. E. kansanum. 

 Stem perennial, evergreen (e.xcept sometimes in E. lacvigatum), mostly simple; spike 

 apiculate, with a rigid tip; stomata in regular rows. 

 Central cavity present; stem more than 6-angied, except sometimes in E. variegatum. 

 Teeth of the sheaths deciduous; stem tall and stout, many-grooved. 

 Stem tubercled, rough. 



Sheath close, usually with a black or dark ring near the base, then grayish 

 and with a narrow dark border at the base of the teeth. 

 Stem 1-2 m. liigh, stout; sheaths as broad as long. 7. E. robusturn. 

 Stem 0.3-1 m. liigh, slender; sheath longer than broad. 



8. E. affine. 



Sheaths more ampliate above, green, with or without a narrow border, 



but no ring below. 9. E. intermedium. 



Stem not tubercled, smooth; sheaths enlarged upwards, with or without a dark 



margin, but rarely with a ring below. 10. E. lacvigatum. 



Teeth of the sheaths persistent, white-margined: stem low, slender, 5-10-grooved. 



11. E. variegatum. 

 Central cavity wanting; stem 0-angled. 12. E. scirpoides. 



Family (3. ISOETACEAE. Quillwort Family. 



1. ISOETES. Quillwort. 



Submerged species; leaves without peripheral bast-bundles. 



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

 combed. 1. 7. occidentalis. 

 Stomata present; macrospores spinulose or tubercled. 



Macrospores spinulose. 2. /. Braunii. 



Macrospores with low tubercles. 3. I. Bolanderi. 



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

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



4. /. Howellii. 

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

 bundles 3. 5. I. NutialUi. 



Family 7. LYCOPODIACEAE. Club-moss Family. 

 1. LYCOPODIUM L. Club-moss, Ground Pine. 



Sporanges borne in the axils of ordinary leaves, which are not arranged in distinct spikes 

 Leaves hollow at base, all or mostly all ascending, of nearly one length. 



1. L Selagn. 

 Leaves flattened, not hollow at base, spreading or deflexed, longer and shorter in 

 alternating zones. 2. L. porophilum. 



Sporanges borne in the axils of bracts arranged in spikes on the aerial branches. 

 Spikes sessile, or with stalks not more than 1 cm. long. 



Aerial branches all simple. 3. L. inundatum. 



Aerial branches, at least in part, branched. 



