1955] 



REVISION OF THE GENUS SAG ITT ARIA 



211 



ends triangular. Stamens (9-)12-18, the filaments ca. 1 mm long. Mature recepta- 

 cle 0.8-1.2 cm in diameter; achenes large, 2.5-3.5 x 1.3-2 mm, the prominent 

 dorsal wing crenate-crested, the faces plain or with 1-3 low ribs, the beak subu- 

 late, to 0.4 mm long, occasionally obsolete. (FIG. llo.) 



Type collection: Curtis 'O, ponds, South Carolina (holotype MO; isotype GH). 

 The type specimen unfortunately is not at all typical of the bulk of the collec- 

 tions, and indeed, comes very close to being intermediate between var. graminea 

 and var. macrocarpa. The large crested achenes are distinctive, however, to serve 

 safely to identify the type specimen and other intermediates as var. macrocarpa. 



Distribution: North and South Carolina. A local plant of the highlands, but not 

 the mountains, present in bogs, ponds, and sluggish streams. All the collections 

 seen appear to be confined to Henderson Co., North Carolina and vicinity, except 

 for the type collection which is labelled "South Carolina." (FIG. 11.) 



Sagittaria graminea is the only member of the genus with pubescent, dilated 

 filaments. It apparently hybridizes with all other Sagittarias that have pubescent 

 filaments and occur within its range, including S. rigida and S. lancifolia, both of 

 which are closely related to it, and montevidensis from which it may have 

 evolved. 



In a genus characterized by variable species, S. graminea probably represents 

 the high tide of that variability. Every characteristic is extremely plastic and it 

 is the exception rather than the rule that enough variable factors become cor- 

 related in a geographic pattern to warrant the formation of a separate taxon. Al- 

 together six varieties in addition to var. graminea are here recognized. All have 

 been treated at one time or another as separate species, but careful study of 

 some 1200 collections shows no basis for following this course. All these varie- 

 ties fall entirely within the range of S. graminea var. graminea, but otherwise 

 none of them ever encroaches on the geographic distribution of any other. Each 

 shows some intergradation in its own range with var. graminea, and certain plants 

 of similar appearance may occur in populations of var. graminea well removed 

 from its accepted range. At the same time the extremes of these taxa are certainly 

 distinctive and could not, except in a most juvenile state, be confused with var. 

 graminea. Actually, then, the well-marked geographic isolates have been separated 

 out as varieties, and the remainder included in var. graminea. The latter, therefore, 

 is of necessity the most plastic variety and includes many incipiently variable 

 plants as well as the numerous, intermediate forms. 



The variety platyphylla of the Gulf and south°central states is easily recog- 

 nized by the recurved pistillate pedicels. It probably arose as a result of hybridi- 

 zation between S. graminea and S. montevidensis subs p. calycina, with subsequent 

 introgression with S, graminea. It shows signs of being intermediate in bract, 

 filament, and achene characteristics and has pistillate pedicels which resemble 

 those of S. montevidensis . In all other respects it approaches S, graminea. A 

 narrow-leaved form in Alabama has been called S, mohrii but is not tenable as a 

 taxon. 



The var. teres of Cape Cod, Long Island, and the pine barrens of New Jersey 

 shows differences that come close to being specific. The small, fully connate 

 bracts, the crenate-winged achenes, and the peculiar spongy-terete phyllodia are 

 all quite distinct. 



The var. weatherbiana of the southeastern coastal plain is less distinctive. In 

 general it is larger in all respects than var. graminea. Its unique production of 

 leaves in the fall and the early spring flowering and fruiting make it seem worthy 

 of separation. 



