2955] 



REVISION OF THE GENUS SAG ITT ARIA 



203 



prominently veined, sagittate, emersed leaves, and in the recurved, thickened, 

 pistillate pedicels. The bracts of 5. intermedia are much reduced in size, how- 

 ever, and the tuberculate, short-beaked achenes and small, spreading sepals of 

 the mature pistillate flowers are quite distinct. 



The species shows a wide tolerance for varying edaphic conditions, seemingly 

 growing as well in a salt pond as in an inland bog. The plasticity of leaf-shape 

 is possibly correlated with the wide range of habitats. S. intermedia and S. land- 

 folia are the only members of the genus found throughout the West Indies, if one 

 exlcudes the infrequently collected and only doubtfully indigenous S. latijolia, 



7. Sagittaria demersa J.G.Sm. Missouri Bot. Gard. Rep. 6: 32. 1894. 



Fibrous-rooted annual, or perennating by runners. Leaves reduced to sub- 

 merged phyllodia 10-45 cm long, typically narrowing toward the free ends, these 

 floating and occasionally widened to 0.5 cm. Scape simple, weak, with 3-5 whorls 

 of flowers, these floating. Bracts about 0.4 cm long, connate, sheathing, scarious 

 margined, soon evanescent. Pistillate flowers with thickened recurved pedicels 

 2.0-3.0 cm long; sepals about 0.4 cm long, spreading at maturity; petals white, 

 about 1.5 times as long as the sepals. Staminate flowers with filiform more or 

 less ascending pedicels 0.8-1.2 cm long; stamens 12-15, the glabrous filaments 

 about 0.8 mm long, dilated below, abruptly contracted above, the oblong anthers 

 about 0.5 rnm long. Mature pistillate heads 0.5-0.6 cm in diameter; achenes 

 obovate, 1.6-2.0 x 0.9-1.2 mm, the wings narrow, the faces unadorned, the fili- 

 form beak about 0.5 mm long, obliquely to vertically inserted. (FIG. 9a.) 



Type collection: Pringle 1367, pond near Guerrero, Chihuahua, Mexico (holo- 

 type NY, isotypes GH, MEX, NY, US). 



Distribution: Ponds and lakes of the Mexican highlands. (FIG. 9.) 



MEXICO. Chihuahua: La Junta, LeSeuer 273 (GH). Hidalgo: Lake Apam, Apam, H. E. 

 Moore 3454 (GH, US). 



A species of limited geographic range, collected only three times, these sta- 

 tions some 500 miles apart in the Mexican highlands. It probably is present, and 

 should be sought, at intermediate points. While it must be considered a very 

 local plant, it is extremely abundant where found; Moore describes it as forming 

 great masses. S. demersa shows relationship with both S. montevidensis subsp. 

 calycina and 5". subulata, and may be intermediate between these two species. It 

 may be distinguished from S, montevidensis by the spreading, small sepals of the 

 pistillate head, from S. subulata by the scarious-margined, sheathing, connate 

 bracts, and from both by the filiform beak of the unadorned achene. 



8. Sagittaria subulata (L.) Buch. Abh. Nat. Ver. Brem. 2: 490. 1871. 



Annual, or perennating by runners and corms. Submerged or tidal plant. Leaves 

 reduced to phyllodia 5-90 cm or more long, 0.1-1.4 cm wide, the floating ends 

 occasionally widened into more or less distinct lanceolate to ovate blades 

 2-6x0.5-2.5 cm, rarely cordate or sagittate. Scapes 5-90 cm long or longer, 

 typically simple with 1-10 whorls of flowers, rarely branching from the lowest 

 whorl. Bracts typically connate at the base, sheathing, 0.2-0.4 cm long, some- 

 what scarious margined, the caudate ends to 3 cm long, occasionally spathe-like, 

 soon evanescent. Pistillate flowers with variously thickened recurved pedicels 



Explanation of Figures 9> 10 



FIG. 9. Distribution of two Mexican species of Sagittaria, a, achene of S. demersa, 

 X 3. b-d, S. macrophylla. b, achene, X 3. c, stamen, X 3. d, bracts, X 2 / 3 . FIG. 10. Dis- 

 tribution of S. subulata. a-c, var. subulata. a, achene, X 3. b, bracts, X 1. c, stamen, 

 X 3. d, bracts of var. gracillima, X %. e, bracts of var. kurziana, X %. 



