5(3). Leaflets usually more than 10 mm. long, truncate and typically irregularly 

 toothed at apex 5. M. tenuifolia. 



5. Leaflets less than 8 mm. long, lightly rounded to subtruncate and entire at 

 apex 6. M. Fournieri. 



1. Marsilea macropoda Engelm. ex A. Br. Fig. 9. 



Plants robust, 10-25 cm. tall, forming large mats, adorned with bright red- 

 dish hairs at the tips of the branches of the subglabrous rhizomes; petioles slender, 

 with long shaggy hairs; leaflets large, broadly cuneate, entire, usually undulate, 

 clothed on both side with long lax whitish hairs (especially when young), becom- 

 ing less pubescent with age, to 5 cm. long and 2 cm. wide; sporocarps 2 to 6 on 

 erect or ascending branched peduncles that are 2—3 cm. long, obliquely obovate, 

 densely villous with the reddish hairs to 3 mm. long or more, 6-8 mm. long, 5-6 

 mm. in diameter, the raphe short, lower tooth obtuse, upper tooth inconspicuous 

 or wanting; sori 10 in each valve. 



In mud or sandy soil and water of swamps, marshes, woodland bogs, ditches, 

 streams, and on the edge of ponds and lakes, apparently endemic to Tex. where 

 it is widespread and rather frequent in the Rio Grande Plains, n. and e. to 

 Jackson Co. in the Coastal Prairies, Travis Co, in the Blackland Prairies, and 

 in the cos. bordering the Edwards Plateau. 



The several sporocarps borne on each peduncle and the large hairy leaflets are 

 characteristics that readily distinguish this species. 



2. MarsUea mexicana A. Br. Fig. 4. 



Plants to 2 dm. tall or more; rhizomes slender, widely creeping and much- 

 branched, greenish-brown to light-brown; petioles filiform, channeled, glabrous, 

 to about 18 cm. long; leaflets broadly cuneiform or obovate-flabellate, rounded 

 and slightly undulate at apex, 1—1.5 cm. long, green, typically marked with 

 reddish-brown stripes (or glands?) parallel with the veins on the lower surface, 

 glabrous or sometimes with a few hairs near base; peduncle (free part) approxi- 

 mately as long as the sporocarp or slightly longer, pubescent at first; sporocarps 

 not scattered but densely clustered on special branchlets that also give rise to slender 

 terete rigid rootlike structures, obovoid to ellipsoid, about 4 mm. long, somewhat 

 compressed laterally, dark-colored, at first covered with matted light-brown hairs 

 and terminated with long dark-brown hairs that are deciduous with age, the 

 raphe and basal tooth obsolescent; sori approximately 12 or 13 in each sporocarp. 



In shallow water or on mud flats of pools and ponds in Aransas Co. on the 

 Tex. coast; from Tex. and Mex., s. to Hond. 



This species is distinctive in that at least some of its leaflets have reddish- 

 brown stripes, or possibly glands, on their lower surface parallel with the veins. 

 Also, the sporocarps are borne in clusters on modified branchlets that also give 

 rise to terete, rigid, rootlike structures that possibly might be considered as 

 rhizophores. 



3. Marsilea mucronata A. Br. Hairy pepperwort. Figs. 9 and 11. 



Plants 6-20 cm. tall; rhizomes slender, widely creeping, branched but without 

 conspicuous fascicled branches; petioles filiform, to 18 cm. long; leaflets spreading, 

 spatulate to obovate, truncate to rounded and entire or somewhat toothed at the 

 apex, sparsely pubescent (especially beneath) with short and broad appressed 

 hairs, to 15 mm. long, about as wide as long; peduncles free, axillary at base 

 of leaves or from the very base of the petiole, ascending, usually very short, mostly 

 scarcely as long as the sporocarp; sporocarps solitary, oval to ellipsoid, slightly 

 oblique and compressed, purplish punctate, coarsely strigose-pubescent with red- 

 dish hairs, to 8 mm. long, usually much smaller, 3-6 mm. in diameter, the raphe 



55 



