The Manual of the Botany of the Northern United States Part 215

9. L. complanatum, L. (GROUND-PINE.) Stems extensively creeping (often subterranean), the erect or _ascending branches several times forked above_; bushy _branchlets crowded, flattened_, fan-like and spreading, _all clothed with minute imbricated-appressed awl-shaped leaves in 4 ranks_, with decurrent-united bases, the lateral rows with somewhat spreading tooth-like tips, those of the upper and under rows smaller, narrower, wholly appressed; peduncle slender, _bearing 2--4 cylindrical spikes_.--Var. CHAMaeCYPARiSSUS has narrower, more erect and bushy branches, and the leaves less distinctly dimorphous.--Woods and thickets; common, especially northward. (Eu.)

ORDER 134. SELAGINELLaCEae.

Leafy plants, terrestrial or rooted in mud, never very large; the stems branching or short and corm-like; the leaves small and 4--6-rowed, or subulate and elongated; sporangia one-celled, solitary, axillary or borne on the upper surface of the leaf at its base and enwrapped in its margins, some containing large spores (_macrospores_) and others small spores (_microspores_). The macrospores are in the shape of a low triangular pyramid with a hemispherical base, and marked with elevated ribs along the angles. In germination they develop a minute prothallus which bears archegonia to be fertilized by antherozoids developed from the microspores.

1. Selaginella. Terrestrial; stems slender; leaves small; sporangia minute and axillary.

2. Isoetes. Aquatic or growing in mud; stems corm-like: leaves elongated and rush-like; sporangia very large, enwrapped by the dilated bases of the leaves.

1. SELAGINeLLA, Beauv. (Pl. 21.)

Fructification of two kinds, namely, of minute and oblong or globular spore-cases, containing reddish or orange-colored powdery microspores; and of mostly 2-valved tumid larger ones, filled by 3 or 4 (rarely 1--6) much larger globose-angular macrospores; the former usually in the upper and the latter in the lower axils of the leafy 4-ranked sessile spike, but sometimes the two kinds are on opposite sides all along the spike.

(Name a diminutive of _Selago_ an ancient name of a Lycopodium, from which this genus is separated, and which the plants greatly resemble in habit and foliage.)

[*] _Leaves all alike and uniformly imbricated; those of the spike similar._

1. S. spinsa, Beauv. _Sterile stems prostrate_ or creeping, small and slender; _the fertile thicker, ascending, simple_ (1--3' high); _leaves lanceolate, acute, spreading, spa.r.s.ely spinulose-ciliate_. (S.

selaginoides, _Link._)--Wet places, N. H. (_Pursh_), Mich., Lake Superior, Colorado, and northward; rare.--Leaves larger on the fertile stems, yellowish-green. (Eu.)

2. S. rupestris, Spring. (Pl. 21, fig. 1--4.) _Much branched in close tufts_ (1--3' high); _leaves densely appressed-imbricated, linear-lanceolate_, convex and with a grooved keel, _minutely ciliate, bristle-tipped_; those of the strongly quadrangular spike rather broader.--Dry and exposed rocks; very common.--Grayish-green in aspect, resembling a rigid Moss. Very variable farther west and south. (Eu.)

[*][*] _Leaves shorter above and below, stipule-like; the lateral larger, 2-ranked._

3. S. apus, Spring. Stems tufted and prostrate, creeping, much branched, flaccid; leaves pellucid-membranaceous, the larger spreading horizontally, ovate, oblique, mostly obtuse, the smaller appressed, taper-pointed; those of the short spikes nearly similar; larger spore cases copious at the lower part of the spike.--Low, shady places; not rare, especially southward.--A delicate little plant, resembling a Moss or Jungermannia.

2. ISETES, L. QUILLWORT. (Pl. 21.)

Stem or trunk a fleshy more or less depressed corm, rooting just above its 2-lobed (or in many foreign species 3-lobed) base, above covered with the dilated and imbricated bases of the awl-shaped or linear somewhat quadrangular leaves, which include four air-tubes, intercepted by cross part.i.tions. Sporangia pretty large, orbicular or ovoid, plano-convex, very thin, sessile in the axils of the leaves, and united at the back with their excavated bases (the thin edges of the excavation folding round partly cover them, forming the _velum_), traversed internally by transverse threads; those of the outer leaves filled with large spherical macrospores, their whitish crustaceous integument marked by one circular, and on the upper surface by three radiating elevated lines (circ.u.mscribing a lower hemisphere, and three upper segments which open valve-like in germination); those of the inner leaves filled with very minute and powdery grayish microspores; these are always obliquely oblong and triangular.--Mostly small aquatics, gra.s.s-like or rush-like in aspect, some always submerged, others amphibious, a few living in merely moist soil, maturing their fruit in late summer and early autumn, except n. 7 and some forms of n. 6.

This genus is left essentially as it was elaborated for the 5th edition by the late Dr. GEORGE ENGELMANN. The present editor has added to the range of a few species, and given var. robusta of n. 3.

[*] _Growing under water, only accidentally or in very dry seasons out of water; leaves without stomata (except in forms of n. 3) and peripherical bast-bundles._

1. I. lacustris, L. (Pl. 21, fig. 1--5.) Leaves (10--25 in number, 2--6'

long) dark green, rigid; sporangium ovoid or circular, the upper third, or less, covered by the velum, the free part pale and unspotted; both kinds of spores the largest of our species; macrospores (0.32--0.38"

wide) covered with short and twisted crested ridges, which often anastomose; microspores (0.017--0.020" long) smooth.--Mountain lakes, Penn., N. Y., and New Eng. to Lake Superior, and northward, often with n. 3. (Eu.)

2. I. Tuckermani, Braun. Leaves (10--30, 2--3' long) very slender, awl shaped, olive-green, the outer recurved; sporangium ovoid or circular, the upper third covered by the velum, the free part sometimes brownish-spotted; macrospores (0.22--0.28" wide) on the upper segments covered with parallel and anastomosing ridges, the lower half reticulated; microspores (0.013--0.015" long) smooth or very delicately papillose.--Mystic and other ponds near Boston, together with the next (_Tuckerman, W. Boott_).

3. I. echinospora, Durieu. Leaves slender, awl-shaped; sporangium ovoid or circular; macrospores (0.20--0.25" wide) beset all over with small entire and obtuse or slightly forked spinules. (Eu.)--In this European form, the leaves are very slenderly attenuated (3--4' long), the upper margin of the sporangium only is covered with the narrow velum, the free part is unspotted, and the slightly papillose microspores are larger (0.015--0.016" long).

Var. Braunii, Engelm. Leaves (15--30 in number, 3--6' long) dark and often olive-green, straight or commonly recurved, half or two thirds of the sporangium covered by the velum, the free part often with light brown spots; macrospores as in the type; microspores smaller (0.013--0.014" long), smooth. (I. Braunii, _Durieu._)--Ponds and lakes, New Eng. to N. Y., Penn., Mich., and northward, often with the two preceding.--Frequently with a few stomata, especially in Niagara specimens.

Var. robusta, Engelm. Stouter; leaves (25--70, 5--8' long) with abundant stomata all over their surface; velum covering about one half of the large spotted sporangium; macrospores 0.18--0.27" wide.--Lake Champlain, north end of Isle La Motte (_Pringle_).

Var. muricata, Engelm. Leaves (15--30, 6--10' long) straight or flaccid, bright green; about one half of the almost circular sporangium covered by the velum, unspotted; macrospores (0.22--0.27" wide) with shorter and blunter spinules; microspores as in the last variety, or rarely spinulose. (I. muricata, _Durieu._)--In some ponds north of Boston (_W.

Boott_).

Var. Boottii, Engelm. Leaves (12--20, 4--5' high) awl shaped, stiffly erect, bright green, with stomata; sporangium as in the last; macrospores as in the type, but a little smaller and with very slender spinules. (I. Boottii, _Braun_, in litt.)--Pond in Woburn, near Boston, partly out of water (_W. Boott_).

[*][*] _Growing partly out of water, either by the pond drying up or by the receding of the ebb tide; leaves with stomata, and in n. 6 and 7 with four or more peripherical bast-bundles._

4. I. saccharata, Engelm. Leaves (10--15, 2--3' long) slender, olive-green, curved; sporangium small, ovoid, only the upper edge covered by the velum, nearly unspotted; macrospores (0.20--0.22" wide) minutely tuberculate; microspores (0.012" long) papillose.--On Wicomico and Nantic.o.ke Rivers, eastern sh.o.r.e of Maryland, between high and low tide (_Canby_).

5. I. riparia, Engelm. Leaves (15--30, 4--8' long) slender, deep green, erect; sporangium mostly oblong, upper margin to one third covered by the velum, the free part spotted; macrospores very variable in size (0.22--0.30" wide), the upper segments covered by short crested ridges, which on the lower hemisphere run together forming a network; microspores larger than in any other species except n. 1 (0.013--0.016"

long), mostly somewhat tuberculated.--Gravelly banks of the Delaware, from above Philadelphia to Wilmington, between flood and ebb tide; margins of ponds, Lake Saltonstall, Conn. (_Setch.e.l.l_), and northward.--Distinguished from the nearly allied I. lacustris by the stomata of the leaves, the spotted sporangium, the smaller size of the macrospores and their reticulation on the lower half.

6. I. Engelmanni, Braun. Leaves long (25--100, 9--20' long), light green, erect or at last prostrate, flat on the upper side; sporangium mostly oblong, unspotted, the velum very narrow; macrospores (0.19--0.24" wide) covered all over with a coa.r.s.e honeycomb-like network; microspores (0.012--0.014" long) mostly smooth.--Shallow ponds and ditches, from Ma.s.s. (near Boston, _W. Boott, H. Mann_) and Meriden, Conn. (_F. W. Hall_), to Penn. and Del. and (probably through the Middle States) to Mo.--By far the largest of our species, often mature in July.

Var. gracilis, Engelm. Leaves few (8--12 only, 9--12' long) and very slender; both kinds of spores nearly as in the type.--Southern New Eng.

(Westville, Conn., _Setch.e.l.l_) and N. J. (_Ennis_); entirely submersed!

Var. valida, Engelm. Trunk large and stout (often 1--2' wide); leaves (50--100, even 200, 18--25' long) with an elevated ridge on the upper side; sporangium oblong or linear-oblong (4--9" long), {1/3}-- or more covered by the velum; spores very small; macrospores 0.16--0.22" wide; microspores 0.011--0.013" long, spinulose.--Del. (_Canby_) and Penn.

(_Porter_). Sept.

7. I. melanopoda, J. Gay. Leaves (15--50, 6--10' long) very slender, keeled on the back, straight, bright green, usually with dark brown or black shining bases; sporangium mostly oblong, with a very narrow velum, brown or spotted; macrospores very small (0.14--0.18" wide), smoothish, or with faint tubercles or ridges; microspores (0.010--0.012" long) spinulose.--Shallow ponds, and wet prairies and fields, central and northern Ill. (_E. Hall, Vasey_), and westward. June, and sometimes again in Nov.--Trunk more spherical and more deeply 2-lobed, and both kinds of spores smaller than in any other of our species; leaves disappearing during the summer heat. Closely approaching the completely terrestrial species of the Mediterranean region.

ORDER 135. MARSILIaCEae.

Perennial plants rooted in mud, having a slender creeping rhizome and either filiform or 4-parted long-petioled leaves; the somewhat crustaceous several-celled sporocarps borne on peduncles which rise from the rhizome near the leaf-stalks, or are more or less consolidated with the latter, and contain both macrospores and microspores.

1. MARSLIA, L. (Pl. 25.)

Submersed or emersed aquatic plants, with slender creeping rootstocks, sending up elongated petioles, which bear at the apex a whorl of four nervose-veined leaflets, and at or near their base, or sometimes on the rootstock, one or more ovoid sporocarps. These sporocarps or fruit usually have two teeth near the base, and are 2-celled vertically, with many transverse part.i.tions, and split or burst into 2 valves at maturity. The sporocarps have a ring along the edges of the valves, which at length swells up and bears the sausage-shaped compartments from their places. The compartments contain macrosporangia and microsporangia intermixed. (Named for _Aloysius Marsili_, an early Italian naturalist.)

1. M. quadriflia, L. Leaflets broadly obovate-cuneate, glabrous; sporocarps usually 2 or 3 on a short peduncle from near the base of the petioles, pedicelled, glabrous or somewhat hairy, the basal teeth small, obtuse, or the upper one acute.--In water, the leaflets commonly floating on the surface; Bantam Lake, Litchfield, Conn., and now introduced in many places. (Eu.)

2. M. vestta, Hook. & Grev. Leaflets broadly cuneate, usually hairy, entire (2--7" long and broad); petioles 1--4' long; peduncles free from the petiole; sporocarps solitary, short-peduncled (about 2" long), very hairy when young; upper basal tooth of sporocarp longest, acute, straight or curved, lower tooth acute, the sinus between them rounded.

(M. mucronata, _Braun_.)--In swamps which become dry in summer; Iowa and southwestward.

ORDER 136. SALVINIaCEae.

Floating plants of small size, having a more or less elongated and sometimes branching axis, bearing apparently distichous leaves; sporocarps or conceptacles very soft and thin-walled, two or more on a common stalk, one-celled and having a central, often branched receptacle which bears either macrosporangia containing solitary macrospores, or microsporangia with numerous microspores.

1. AZoLLA, Lam. (Pl. 21.)

Small moss-like plants, the stems pinnately branched, covered with minute 2-lobed imbricated leaves, and emitting rootlets on the under side. Conceptacles in pairs beneath the stem; the smaller ones acorn-shaped, containing at the base a single macrospore with a few corpuscles of unknown character above it; the larger ones globose, and having a basal placenta which bears many pedicellate microsporangia which contain ma.s.ses of microspores.

1. A. Caroliniana, Willd. Plants somewhat deltoid in outline (4--12"

broad), much branched; leaves with ovate lobes, the lower lobe reddish, the upper one green with a reddish border; macrospores with three attendant corpuscles, its surface minutely granulate; ma.s.ses of microspores glochidiate.--Floating on quiet waters, from Lake Ontario westward and southward,--appearing like a reddish hepatic moss.