54 Karl M. Wiegand and Arthur J. Eames 



c. Blade obtuse, very large; middle lobe 1-1.3 times as long as broad. 



2a. S. I'., var. obtusa 



a. Leaves not sagittate, or occasionally with very short and narrow basal lobes ; 



fertile heads nearly or quite sessile, with long styles. (S. graminca, which should 



occur in sandy ponds in this flora, has slendcr-pedicelled heads and minute 



styles). 3. S. heterophylla 



1. S. cuneata Sheldon. (Sec Britton & Brown, 111. Fl. S. arifolia Nutt.) Arrow- 



leaf. Arrow-head. 



Alluvial mucky marshes ; scarce. July-Aug. 



Spencer Lake; Jennings Pond; Inlet Marshes, near L. V. R. R. roundhouses; mouth 

 of Fall Creek; Farley Point; outlet of North Spring, Union Springs; Black Lake; 

 Crusoe Prairie. 



Que. to Mich., N. Dak., and B. C. ; southw. to cent. Me., Conn., N. Y., Kans., N. 

 Mex., and Calif. ; rare or absent on the Atlantic Coastal Plain. 



In deep water, ribbon-like phyllodia are frequently produced. 



2. S. latifolia Willd. (S. variabilis of Cayuga Fl.) Arrow-leaf. Arrow-head. 

 Ditches, shores, and marshes, in mucky or gravelly, often alluvial, soil, apparently 



with little reference to lime content ; common. July-Aug. 



N. S. to B. C, southw. to Fla., Mex., and Calif., including the Atlantic Coastal 

 Plain. 



The leaf outline of this plant varies greatly with the depth of the water and 

 exposure to wave action, the form with narrower leaves being found in deep water. 

 Forms intergrading between those with broad leaves and those with narrow leaves 

 are often found in the same colony. The extremely narrow-leaved form, with linear 

 lobes 7 mm. broad or less, is forma gracilis (Pursh) Robinson. Occasionally this 

 form seems to be independent of the depth of the water. In deep water, phyllodia are 

 occasionally developed in this species. The forma diver sifolia (Engelm.) Robinson is 

 an occasional variant from both typical S. latifolia and forma gracilis. 



2a. S. latifolia Willd., var. obtusa (Muhl.) Wiegand. (Rhodora 27:186. 1925.) 

 Ditches and swales about the larger lake marshes, occasionally elsewhere ; common. 



Aug. 



Spencer Lake; Inlet Marshes (D.\) ; Fall Creek, swale below Varna; e. of Etna; 



Cayuga Marshes (D. !) ; Black Lake; Crusoe Lake. 



This is the largest and most distinct form, though occasionally it is almost equaled 



in size by typical 5". latifolia. Its leaf outline is like that of var. pubescens (Muhl.) 



J. G. Sm. Brackish conditions may influence its distribution. 



3. S. heterophylla Pursh. 



Shores of the larger lakes, and in the larger marshes adjoining, rarely elsewhere, 

 preferring rich gravelly or silty, often calcareous, soils ; locally abundant. July-Sept. 



Spencer Lake; Summit Marsh (D.\) ; frequent near Cayuga Lake (D. !) ; Inlet 

 Marshes; Union Springs; Cayuga Marshes (D.\). 



Que. to Minn., southw. to Fla. and Nebr. A plant primarily of the interior. 



The vars. elliptica, rigida, and angustifolia are environmental forms due to depth 

 of water and wave action, and are scarcely worthy of nomenclatorial recognition. 



17. HYDROCHARITACEAE (Frog's Bit Family) 



a. Leaves small, whorled, cauline; spathes sessile or nearly so; tube of perianth of 

 pistillate flowers elongating immensely with depth of water. 1. Elodea 



a. Leaves elongated, ribbon-like, basal ; spathes peduncled, the stalk of the pistillate 

 inflorescence very long, coiled, and reaching the surface ; perianth without a 

 tube. 2. Vallisneria 



