several very minute teeth; intravaginal scales filiform, less than I mm. long; stami- 

 nate flowers 2.5-3 mm. long, the anther 1 -celled; pistillate flowers about 3 mm. 

 long; stigmas 2 to 4, usually 3; seed narrowly elliptic to lanceolate-ovoid, about 

 3 mm. long, apparently smooth and shining but finely reticulate under magnifica- 

 tion. 



In fresh to somewhat brackish water, reported by Mason from w. Ariz., May- 

 Aug.; n, e. Can, to B. C, s. to Md., Ariz, and Calif.; also Eur. 



The occurrence of this species in our region needs verification. We have seen 

 no material. 



Fam. 19. Posidoniaceae Lotsy 



Submerged marine perennials; rhizome and stem densely covered with the per- 

 sistent fibrous leaf bases; leaves sheathing at the base, the sheaths open and ligulate; 

 blades linear, flat, rounded at the apex, leathery, entire to serrulate; flowers perfect, 

 spicate, on long axillary and terminal peduncles; spikes several, subtended by 

 reduced leaves; floral bracts absent; perianth absent or of 3 caducous scales; sta- 

 mens 3 or 4, hypogynous; anthers extrorse, large, sessile, with a thick connective 

 produced beyond the cells, the latter widely separated; pollen threadlike; ovary 

 superior, l-ceUed, with a sessile lacerate or muricate stigma; ovule elongated, 

 parietal, the micropyle inferior; fruit ovoid, fleshy, indehiscent; seed without endo- 

 sperm; embryo with a straight cotyledon. 



A monotypic family, considered to be confined to Australia and the Mediter- 

 ranean region. 



1. Posidonia Konig. 



A genus of 2 species. Characters of the family. Sometimes placed in the Naja- 

 daceae or Potamogetonaceae. 



1. Posidonia Oceania Konig. Fig. 53. 



Characterized by the rhizome and stem being densely covered with the per- 

 sistent fibrous leaf bases; leaves linear, rounded at apex, to 5 dm. long and 7 mm. 

 wide, about 13-nerved; inflorescence a 3-flowered spike, 2 flowers of which are 

 perfect and one staminate; staminal connective broad, abruptly long-aristate; fruit 

 semioval, fleshy, indehiscent. 



This species is included here with some reservations since it is known from 

 Texas only by plants being washed up on the beaches along the coast in Cameron, 

 Galveston and Nueces counties. Since, however, species in the marine genera 

 Cymodocea, Halodule, Thalassia and Halophila are not only frequent in sea drift 

 but are also known to grow along the Texas coast, it is quite possible that Posi- 

 donia may also eventually be found to grow along the Texas coast. 



Fam. 20. Juncaginaceae Rich. Arrow-weed Family 



Annual or perennial marsh herbs from rhizomes or tubers; leaves basal, linear, 

 sheathing, ours with blade terete or semiterete; inflorescence a spikelike raceme 

 borne on a naked scape; flowers with short slender or stout pedicels, unisexual 

 or perfect, regular to slightly irregular, bractless; bractiform perianthlike appen- 

 dages usually 6, in 2 series, each appendage bearing a stamen attached to its base 

 or on some the stamen absent; anthers 2-celled, subsessile, opening by slits; pistil 

 superior, of 6 or 4 (or 3) connate to weakly united carpels, these sometimes sepa- 

 rating in fruit; styles short or absent; stigmas often papillate or plumose; ovule 1 

 per carpel, basal, erect; fruit of distinct or weakly united dehiscent or indehiscent 



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