SALVINIA FAMILY 



35 



Family 4. SALVINIACEAE. 



Salvixia Family. 

 Aquatic, floating plants of small size, with a more or less elongate and some- 

 times branching axis, bearing apparently distichous leaves. Sporocarps (concep- 

 tacles) soft and thin-walled, borne 2 or more on a common stalk, 1-celled, having 

 a central often branched receptacle, this bearing either megasporangia containing 

 a solitary megaspore or microsporangia containing numerous microspores. 



Two genera of wide distribution, Salvinia and the following, each consisting of a few species. 



1. AZOLLA Lam. Encycl. 1 : 343. 1783. 



Fugacious, reddish or green, mosslike plants, with pinnately branched stems covered 

 with minute imbricate 2-lobed leaves, emitting rootlets beneath. Sporocarps of 2 kinds, 

 borne in pairs beneath the stem, the smaller ones ovoid or acorn-shaped, containing at the 

 base a solitary megaspore and a few minute bodies of doubtful function above it ; larger 

 sporocarps globose, with a basal placenta, this bearing many pedicellate microsporangia 

 containing masses of microspores, called massulae. [Greek, signifying killed by drought.] 

 About 5 species of wide distribution, the following the generic type. 



L Azolla filiculoides Lam. 

 Fern-like Azolla. Fig. 72. 



Azolla filiculoides Lam. Encycl. 1: 343. 1783. 



Plants rounded-deltoid or elongate, 1-2.5 cm. 

 broad and long, pinnately branched, with solitary 

 roots, the branches mostly 2-pinnate, often separat- 

 ing and giving rise to new plants ; leaves deeply 

 2-lobed, the dorsal lobe rather thick, green or 

 reddish, with a large cavity in the basal part, 

 papillate-hairy above ; ventral lobe somewhat larger, 

 submersed, 1 cell thick except in the middle. Sporo- 

 , -, carps formed from the ventral lobes of the lowest 

 "^ \ leaves of the branches, subglobose ; megaspores 

 globose, bearing thick cylindrical papillae; massu- 

 lae bearing numerous rigid linear flattish processes 

 I with anchor-like tips. 



Ponds and slow streams, Washington, to southern Cali- 

 fornia and Arizona; Mexico southward, nearly throughout 

 South America. Type locality: Straits of Magellan. 



Family 5. ISOETACEAE.* 

 OuiLLWORT Family. 

 Perennial plants, aquatic to terrestrial in habitat, with 2-3-lobed corm, bearing 

 branched roots and a rosette of erect or recurved sedge-like leaves. Solitary 

 sporangia sessile in leaf axils, of two sorts, microsporangia and megasporangia, 

 producing respectively microspores and megaspores, which, on germination, de- 

 velop gametophytes, the former with a single antheridium, the latter with arche- 

 gonia. 



A family consisting of a single genus, world-wide in distribution. 



1. ISOETES L. Sp. PI. 1100. 1753. 



Submerged, amphibious or terrestrial perennials, with a 2-3-lobed short fleshy stem giv- 

 ing rise to a group of elongated, somewhat triangular or quadrangular leaves, with 4 

 septate longitudinal air-channels, and with or without peripheral strands, with or without 

 stomata. Leaves producing small triangular extension of tissue (ligule) above the single 

 large round or elongated axillary sporangium in basal cavity, more or less encased by 

 membranous extension (velum) on inner face of leaf. Megaspores hemispherical at base, 

 with equatorial ridge, and three other crests joined at apex, with sculptured walls; micro- 

 spores minute, powdery, usually ovoid. [Name Greek, meaning equal at all seasons.] 



About 60 species, of world-wide distribution, of which 20 or more occur in the United States. Type 

 species, Isoetes lacustris L. 



Submersed or rarely emersed; corms 2-lobed; peripheral strands none. 

 Stomata lacking. 



Leaves long; megaspores with irregular network of ridges on basal face, ma.ximum size 640 fi. 



1. 1. occideiitalis. 

 Leaves short: megaspores with points or short ridges, maximum size 800 A- 2. /. piperi. 



*Text contributed by Norm.'\ E. Pfeiffer. 



