An Illustrated Flora of the Northern United States, Canada and the British Possessions/Salviniaceae
Small floating plants with a more or less elongated and sometimes branching axis bearing apparently 2-ranked leaves. Sporocarps soft, thin-walled, borne 2 or more on a common stalk, 1-celled, with a central often branched receptacle, which bears megasporanges containing a single megaspore or microsporanges containing numerous microspores. The megaspores germinate into prothallia which bear archegones, the microspores into prothallia which bear antherids.
The family consists of two genera.
|•||Leaves 6"-9" long, 2-ranked, on mostly simple stems.||1.||Salvinia.|
|•||Leaves minute, closely imbricated on pinnately branching stems.||2.||Azolla.|
Floating annual plants with slender stems bearing rather broad 2-ranked leaves, these finely papillose on the upper surface. Sporocarps globose, depressed, 9-14-sulcate, membranous, arranged in clusters, 1 or 2 of each cluster containing 10 or more sessile megasporanges, each containing a single megaspore, the others containing numerous smaller globose pedicelled microsporanges with very numerous microspores. [Name in honor of Antonio Maria Salvini, 1633-1729, Italian scientist.]
About 13 species widely distributed. Only the following, the generic type, in the United States.
Minute moss-like reddish or green floating plants, with pinnately branched stems covered with minute imbricated 2-lobed leaves, and emitting rootlets beneath. Sporocarps of two kinds borne in the axils of the leaves, the smaller ovoid or acorn-shaped, containing a single megaspore at the base and a few corpuscles above it whose character is not fully known, the larger globose, producing many pedicelled sporanges, each containing several masses of microspores which are often beset with a series of anchor-like processes of unknown function. [Greek, signifying killed by drought.]
About 5 species of wide geographic distribution. Type species : Azolla filiculoides Lam.
|1. Azolla caroliniàna Willd.
Azolla. Fig. 88.
Azolla caroliniana Willd. Sp. Pl. 5: 541. 1810.
Plants greenish or reddish, deltoid or triangularovate in outline, pinnately branching, sometimes covering large surfaces of water. Leaves with ovate lobes, their color varying somewhat with the amount of direct sunlight, the lower usually reddish, the upper green with a reddish border. Megaspores minutely granulate, with three accessory corpuscles; masses of microspores armed with rigid septate processes.
Floating on still water, Ontario and Massachusetts to British Columbia, south to Florida, Arizona and Mexico. Also in tropical America. Naturalized in lakes on Staten Island, N. Y.