filiform. 2- or 3-cleft; flowers unisexual, in the axils of the leaves; pistillate flowers 

 about 1.5 mm. long, conspicuous as a tuft of white or pinkish plumose stigma lobes; 

 staniinate flowers not seen; fruit 1.5-2 mm. long, minutely glandular. M. proser- 

 pinacoidcs Gill. 



Widely scattered in ponds, ditches, streams and on seepage slopes, introd. in 

 Okla. {fide Waterfall), mainly on the Edwards Plateau and in e. Tex., rare in 

 Ariz. (Pinal Co.), Mar.-May; nat. to S.A., tending to escape from cult, and per- 

 sistent in s. U. S. 



2. Myriophyllum spicatum L. Fig. 567. 



Plant rhizomatous with branching leafy shoots to 2.5 m. long; stems reddish- 

 brown to pinkish-tawny in drying; leaves in whorls of 3 to 5 mostly 1 cm. apart 

 or more on stem, those of the middle whorls usually less than 2.5 cm. long, simply 

 pinnate with 12 or more segments on each side of rachis; leaf segments rarely to 

 1.5 cm. long, regularly placed 1-2.5 mm. apart on rachis; spike to about 15 cm. 

 long, emergent, erect; flowers usually in whorls of 4 in the axils of bracts; all but 

 the lowest bracts essentially entire and shorter than the flowers and fruits, the 

 lowest pectinate to serrate and commonly exceeding the flowers; flowers progressing 

 from 4 basal whorls of pistillate flowers through 1 perfect flower to the upper 

 whorls of staminate flowers with reddish caducous petals about 3 mm. long; sta- 

 mens 8; fruit subglobular, 4-lobed. 



In lakes, ponds and slow-flowing streams in s. and w. Okla. (Cimarron and 

 Comanche cos.), on the e. Edwards Plateau and in s.-cen. Tex. (Burnet, Hays, 

 Colorado and Fayette cos.), n. N.M. (Rio Arriba Co.) and Ariz. (Apache, Coco- 

 nino, Gila, Navajo, Pima and Yavapai cos.), Apr.-Sept.; from s.e. Lab. to Alas., 

 s. to W. Va., Tex., N.M., Ariz, and s. Calif.; nat. of Euras. and N. Afr. 



3. Myriophyllum exalbescens Fern. American milfoil. Fig. 568. 



Stems simple or forked, purple, becoming white when dry; leaves in whorls of 

 3 or 4 mostly 1 cm. apart or more on stem, those of the middle whorls usually 

 3 cm. long or more, simply pinnate with 11 or fewer segments on each side of 

 rachis; leaf segments commonly more than 1.5 cm. long, rather widely and irregu- 

 larly spaced 2-4 mm. apart on rachis; spike almost naked, emergent, erect, to 

 about 15 cm. long; flowers in verticils, the lowermost pistillate, the upper ones 

 staminate. the bracteal leaves shorter than the flowers and fruits; petals oblong- 

 obovate, concave, about 2.5 mm. long; anthers 8; fruits subglobose, very narrowly 

 4-sulcate, 2-3 mm. long, the mericarps rounded on the back, smooth or rugulose. 

 M. spicatum var. exalbescens (Fern.) Jeps. 



In ponds, lakes, irrigation ditches and quiet streams, often somewhat calcareous 

 or brackish, in w. Okla. (Beaver Co.), through cen. Tex. to the Panhandle, N. M. 

 (Grant, Rio Arriba, San Miguel and Sandoval cos.) to Ariz. (Apache and Coco- 

 nino COS.), Apr.-Sept.; from s.e. Lab. to Alas., s. to W. Va., Tex., N. M., Ariz, 

 and s. Calif. 



4. Myriophyllum verticillatum L. Fig. 569. 



Stems simple or with few elongate branches to 25 dm. long, in autumn producing 

 crowded winter-buds 1-2 cm. long; leaves in fours and fives; submersed leaves to 

 45 mm. long, with 9 to 13 opposite or alternate pairs of capillary flaccid divisions 

 to 28 mm. long; emersed leaves and bracts smaller and with coarser divisions or 

 merely pectinate-pinnate; flowers in whorls of 4 to 6, perfect or the lower ones 

 pistillate and the upper staminate; bracteoles palmately 7-lobed, about 0.5 mm. 

 long; petals (merely rudiments in pistillate flowers) spoon-shaped, obtuse, about 

 2.5 mm. long; anthers 8 or 4. about 2 mm. long; fruit subglobose, 2-2.5 mm. long, 

 deeply 4-furrowed, the brown smooth or somewhat tuberculate (in ours) carpels 

 rounded on back. 



1205 



