Part 215 (1/2)

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.