Fontinalis Hedwig, 1801.

The Fontinalaceae is a family of primarily aquatic habitats. Some species can be found in the quiet waters of ponds, and other species occupy the waters of very rapidly flowing rivers and streams. All species of Fontinalis have strongly tristichous leaves, and most of those species have the leaves strongly longitudinally folded along the mid-line. Often the leaves are so strongly folded that the two halves are pressed one side against the other. This latter condition of "carinate leaves" may cause the worker to see the leaf as flat and not-folded, thus interpreting the leaf shape on the basis of the shape of the longitudinally-halved leaf. Effective work on Fontinalis requires the unfolding of the two leaf halves with the placement of that unfolded leaf for viewing under the microscope. Very important, also, is the viewing of the intact plant to see the outline of the keel. A straight keel describes a straight line from the insertion on the stem all the way to the leaf apex. Alternatively, the keel can be curved from base to apex, or it can have a basal curve giving way to a straight distal portion. Fontinalis, with a maximum length of about 1 meter, is the largest moss in the state.

Key to Fontinalis

Mosses treated in this section are aquatic to semiaquatic ecostate mosses with tristichous leaves that are mostly deeply keeled along mid-line.

Species included in this key are all in Fontinalaceae:
Fontinalis antipyretica Hedwig
Fontinalis chrysophylla Cardot
Fontinalis gigantea Sullivant
Fontinalis howellii Renauld & Cardot
Fontinalis hypnoides C. J. Hartman
Fontinalis mollis C. Müller Hal.
Fontinalis neomexicana Sullivant & Lesquereux

A. Leaves not keeled, completely plane and very flaccid .....Fontinalis hypnoides
A. Leaves clearly carinate .....B

B. Leaf keel curved throughout; branch and stem leaves similar in shape and only gradually different in size .....C
B. Leaf, when viewed from the side, showing a nearly straight keel that basally curves abruptly to the point of insertion; branch and stem leaves strongly and abruptly different in size and shape .....F

C. Branch apices spinulose with tightly overlapping immature leaves making a bud-like structure 5-10 times as long as its width at mid-point, triangular in cross-section; plants regularly with sporophytes; perichaetial leaves abruptly apiculate .....Fontinalis neomexicana
C. Branch apices not so strongly resolved into a bud-like structure; perichaetial leaves obtuse .....D

D. Leaves of larger stems broadest near the middle (look at either half of the keeled leaf) .....Fontinalis mollis
D. Leaves broadest near the base, mostly near the point of inflection of the basal curve .....E

E. Leaves (when spread flat) mostly about as broad as long; best-developed leaves at least 5 mm broad .....Fontinalis gigantea
E. Leaves typically nearly twice as long as broad; best-developed leaves less than 5 mm broad .....Fontinalis antipyretica

F. Leaves keeled so that the two lateral halves approach being pressed on one another; branch leaves proportionately more narrow than leaves of stem .....Fontinalis howellii
F. Leaves concave to nearly plane in distal portion; branch leaves markedly more narrow than stem leaves, almost subulate near branch apices .....Fontinalis chrysophylla