SALViNIA NaTANS, L., was said by Pursh to grow floating on the surface of small lakes in Western New York, and has more recently been said to occur in Missouri. It has oblong-oval floating leaves 4--6" long, closely pinnately-veined, which bear conceptacles and branching plumose fibres on their under surface.

SUBCLa.s.s II. CELLULAR ACROGENS, OR BRYOPHYTES.

Plants composed of cellular tissue only. Antheridia or archegonia, or both, formed upon the stem or branches of the plant itself, which is developed from the germinating spore usually with the intervention of a filiform or conferva-like prothallus.--Divided into the _Musci_, or Mosses, and the _Hepaticae_.

DIVISION I. HEPaTICae.[1] (LIVERWORTS.)

[Footnote 1: Elaborated for this edition by Prof. L. M. UNDERWOOD, of Syracuse, N. Y.]

Plants usually proc.u.mbent, consisting of a simple thallus, a thalloid stem, or a leafy axis; leaves when present 2-ranked, with uniform leaf-cells and no midvein; thalloid forms with or without a midvein, smooth or scurfy or scaly beneath and usually with numerous rootlets.

s.e.xual reproduction by antheridia and archegonia, which are immersed in the thallus, or sessile or pedicelled upon it, or borne on a peduncled receptacle. The fertilized archegonium develops into a capsule (_sporogonium_) closely invested by a calyptra, which ruptures above as the ripened capsule (containing numerous spores and usually elaters) pushes upward. It is also commonly surrounded by a usually double involucre, the inner (often called _perianth_) more or less tubular, the outer tubular or more often foliaceous, sometimes wholly wanting.

Propagation is also effected by offshoots (_innovations_), runners (_flagella_), or by _gemmae_, which appear at the margin of the leaves or on the surface of the thallus, often in special receptacles.

ORDER 137. JUNGERMANNIaCEae. SCALE-MOSSES.

Plant-body a leafy axis or rarely thallose. Capsule borne on a slender often elongated pedicel, splitting at maturity into 4 valves. Elaters mixed with the spores, mostly bispiral (unispiral in n. 1--3, 32, and 33, 1--3-spiral in n. 5 and 28). Antheridia and archegonia dicious or moncious, in the latter case either mingled in the same inflorescence, or separated upon the same branch, with the antheridia naked in the axils of the lower leaves, or on separate parts of the same plant.

Leaves 2-ranked, incubous (i.e. the apex of each leaf lying on the base of the next above), or succubous (i.e. the apex of each leaf lying under the base of the next above), or sometimes transverse, with frequently a third row of rudimentary leaves beneath the stem.

Artificial Key to the Genera.

-- 1. Plant-body a leafy axis.

[*] Leaves complicate-bilobed (i.e. folded together) or with a small basal lobe.

[+] Lower lobe smaller than the upper.

[++] Root-hairs borne on the stems or underleaves.

1. Frullania. Lower lobe mostly saccate, more or less remote from the stem. Branches intra-axillary, the leaves on either side free.

2. Jubula. Lower lobe saccate; branches lateral, a basal leaf borne partly on the stem, partly on the branch.

3. Lejeunea. Lower lobe incurved, more or less inflated.

5. Porella. Lower lobe ligulate. Perianth triangular, the third or odd angle ventral.

[++][++] Root-hairs rising from the lower lobes.

4. Radula. Perianth compressed. Underleaves none.

[+][+] Upper lobe smaller than the lower, or the two somewhat equal.

[++] Leaves succubous as to their lower lobes.

15. Scapania. Involucral leaves 2; perianth dorsally compressed, the mouth truncate, bil.a.b.i.ate, decurved.

16. Diplophyllum. Involucral leaves few; perianth erect, round, the mouth denticulate.

[++][++] Leaves transverse.

25. Marsupella. Perianth tubular or somewhat compressed. (Compare also Jungermannia -- Sphenolobus.)

[*][*] Leaves palmately 3--4- (or many-) cleft.

[+] Divisions numerous, capillary. Plants large, usually in conspicuous mats.

6. Ptilidium. Leaves palmatifid with ciliate margins.

7. Trichocolea. Leaves setaceously multifid.

[+][+] Leaves 3--4-cleft or parted; plants small, mostly inconspicuous.

10. Lepidozia. Leaf-divisions two cells wide or more.

11. Blepharostoma. Leaf-divisions only one cell wide.

[*][*][*] Leaves entire, emarginate, or 2--3-toothed or -lobed.

[+] Leaves closely imbricate on short julaceous stems.

27. Gymnomitrium. Involucre double, the inner shorter.

[+][+] Leaves deeply bilobed.

8. Herberta. Underleaves large. Perianth fusiform on an elongated branch.

12. Cephalozia. Underleaves mostly wanting; perianth mostly triangular on a short branch.

[+][+][+] Leaves incubous, mostly plane or depressed.

9. Bazzania. Leaves mostly 2--3-toothed. Perianth fusiform on a short branch.

14. Kantia. Leaves mostly entire. Perianth fleshy, pendulous, subterranean.

[+][+][+][+] Leaves succubous or transverse.

[++] Underleaves entire or nearly so.

13. Odontoschisma. Involucral leaves numerous, small, incised, those of the stem rounded or retuse.

21. Mylia. Involucral leaves 2, connate at base. Large.

22. Harpanthus. Involucral leaves few, smaller than the semi-vertical emarginate stem-leaves. Small.