heads 2-3 cm. in diameter; achenes brown or greenish-brown, prominently stipi- 

 tate, the fusiform body 4-6 mm. long and often constricted at the middle, the 

 beak (including the stigma) 3-5 mm. long. S. simplex of Am. auth., illegit. name. 



Mucky bottoms of shallow ponds, along streams and sloughs, in N.M. (Sando- 

 val, San Miguel and Taos cos.) and Ariz. (Coconino Co.), June-Oct.; La. to Alas., 

 s. to Pa., N.M., Ariz, and Calif.; Euras. 



The North American plant is referred to var. midtipedunculatum (Morong) 

 Reveal [S. multipendimculatum (Morong) Rydb.] with not so strongly keeled 

 basal leaves, somewhat V-shaped in cross section, and with mature achenes 

 (including the stipe and beak) about 10 mm. long. 



4. Sparganium angustifolium Michx. 



Slender usually submersed aquatic, the leaves and stems floating or below the 

 surface, 3-10 dm. long; leaves usually 2-6 mm. wide, often very long, curved on 

 the back; inflorescence usually simple but the lower 1 or 2 pistillate heads long- 

 stalked and borne in the axil or above the axil of a bract; pistillate heads 2 to 4; 

 staminate heads usually 2 to 5, somewhat confluent; perianth scales borne at base 

 of the constricted part of the ovary or at base of stipe; stigma scarcely 1 mm. 

 long; fruiting heads less than 2 cm. in diameter; achenes sessile or stipitate, often 

 both kinds in the same head, the fusiform body 2.5-3 mm. long, the beak (includ- 

 ing stigma) about 2 mm. long. 



Usually in shallow or deep water in high montane lakes in n. N.M. (Rio Arriba 

 and Colfax cos.) and n. Ariz., June-Oct.; Lab. to Alas., s. to Pa., N.M., Ariz, and 

 Calif.; Euras. 



It is quite possible that this concept should be united with S. emersum. Their 

 separation, based primarily on size diff^erences of various organs, is most tenuous. 



5. Sparganium americanum Nutt. Fig. 30. 



Plants stout to slender, to 1 m. tall; leaves soft, thin, flat, translucent, loosely 

 ascending or occasionally floating, to 2 cm. wide; lower bract similar to leaves, 

 spreading-ascending, scarious-margined at base; inflorescence simple or sometimes 

 branched, the heads or branches axillary, the primary axis with 1 to 5 pistillate 

 heads and 5 to 9 staminate heads, the branches (when present) with 1 to 6 

 staminate heads and 1 to 3 (rarely 0) pistillate heads; anthers 0.8-1.2 mm. long; 

 stigma linear-oblong to lanceolate, 1-2 mm. long; fruiting heads 1.5-2.5 cm. in 

 diameter; achenes dull or but slightly lustrous, the body 2 mm. thick, the beak 

 L5-5 mm. long; anthers about 1 mm. long. 



In shallow water in e. Okla. (Delaware and Le Flore cos.) and e. Tex., Apr.- 

 June; from Nfld. to Ont., Wise, Minn, and N. D., s. to Fla., Ala., Tex. and Mo. 



See note under S. androcladum. 



6. Sparganium androcladum (Engelm.) Morong. 



Plants stout, to 12 dm. tall; leaves stiffish, strongly ascending, elongate, nearly 

 flat but keeled below, 4-15 mm. wide; lower bracts similar to the leaves, slightly 

 scarious-margined at base; inflorescence branched or rarely simple, the primary 

 axis with 1 to 4 mostly sessile axillary pistillate heads and 4 to 10 staminate heads, 

 the 1 to 3 filiform strongly arched geniculate branches with 3 to 8 staminate heads 

 and rarely 1 pistillate head; stigma filiform, 2-4 mm. long; fruiting heads 2.5-3.5 

 cm. in diameter; achenes lustrous, the body 2.5-3 mm. thick, the beak 4.5-6 mm. 

 long; anthers 1-1.5 mm. long; receptacle fimbrillate-alveolate. 



In swamps and shallow water of streams in e. Okla. (Ottawa Co.) and e. Tex., 

 Apr.-June; from Que. to Minn., s. to Va., e. Ky., 111., Mo., Okla. and Tex. 



Plants that comprise S. americanum and 5". androcladum, which have the heads 

 or branches of their inflorescence all axillary, are restricted in our area to eastern 

 Oklahoma and eastern Texas. Voucher specimens of plants that we have examined, 



93 



