filiform, to about 7 cm. long, villous but eventually glabrescent; leaflets asym- 

 metric, cuneate-oblanceolate to cuneate-obovate or linear-oblanceolate, sub- 

 truncate to lightly rounded at the entire apex, about 7 mm. long, villous; peduncle 

 shorter than the sporocarp; sporocarps crowded, broadly ellipsoid to suborbicular- 

 oval, lightly compressed, invested with brownish hairs that soon turn grayish and 

 are eventually deciduous, about 4 mm. long, the raphe short and blunt, the upper 

 tooth sharp and prominent; sori 15, with 4 to 7 white sporangia in each sorus. 



In wet places or depressions such as playa lakes that are periodically inundated, 

 rare in N.M. (Lea Co.), more frequent in Mex. (Coah., Chih., S.L.P. and Jal.); 

 to be expected in Tex. 



2. Filuiaria L. Pillwort 

 Six widely distributed species. 



1. Pilularia americana A. Br. American pillwort. Fig. 7. 



Very small inconspicuous plants of muddy situations, with slender wide-creeping 

 rhizomes bearing at the nodes one to several leaves, forming dense mats; leaves 

 setiform, solitary or sometimes several together from the nodes, glabrous, 2-6 cm. 

 long, rarely to 1 dm. long; sporocarps produced just below surface of ground, 

 axillary, pedunculate, globose, brownish-yellow, 2-3 mm. in diameter. 



In shallow temporary muddy pools on rock flats and depressions in clayey 

 prairies and in mud on edge of lakes, in our region only in Comanche Co. in s. w. 

 Okla. and in Burnet Co. on the Edwards Plateau in Tex.; from s. Calif, to Ore.. 

 also isolated in s.-cen. Kan., w. Ark. and cen. Ga. 



Fam. 9. Salviniaceae Dum. Salvinia Family 



Plants minute or small, aquatic, free-floating or on mud, with a branched 

 rhizome bearing simple roots (Azolla) or essenti&l'v stemless with some of the 

 leaves modified as roots (Salvinia); leaves 2-ranked or in whorls, opposite or 

 alternate, simple or lobulate; sporocarps soft, thin-walled, borne singly or two or 

 more on a common stalk at the base of the leaves, 1 -celled, with a central often 

 branched receptacle, unisexual, bearing either megasporangia containing a 

 solitary megaspore or microsporangia containing numerous microspores; massulae 

 within macrosporangia bearing septate or non-septate glochidia with barbed tips; 

 megaspores germinate into prothallia bearing archegonia; microspores germinate 

 into prothallia bearing antheridia. 



This family comprises 2 genera of wide distribution — Salvinia and Azolla with 

 about 16 species. 



1. Azolla Lam. Water Fern. Mosquito Fern 



Minute reddish or green free-floating plants, occasionally on mud, mostly 

 densely matted and resembling some species of liverworts, with the stems pinnately 

 branched and concealed by pendent roots and imbricating leaves; leaves distichous, 

 2-lobed, with the upper lobe floating and the lower lobe submersed; sporocarps 

 borne in one or two pairs on the lower leaf lobe. 



This genus consists of about 6 species of wide distribution. 



The dense cover often formed by these plants over the surface of ponds and 

 lagoons provides shade and shelter for fish. The plants are incidentally eaten by 

 ducks and other wild fowl. 



A compound microscope is needed in order to identify species in this genus 

 with any certainty. 



57 



