190 Karl M. Wiegand and Arthur J. Eames 



4. P. lapathifolium L. (P. incaniatum of Cayuga Fl.) 



Damp gravelly stream banks and lake shores, in nonacid soils ; not uncommon. 

 July-Sept. 



Coy Glen ; along the Inlet ; Inlet Marshes ; Cayuga Lake shore ; Fall Creek ; Dryden 

 Lake ; Montezuma Marshes ; and elsewhere. 



Throughout temperate N. A., occurring sparingly on the Atlantic Coastal Plain. 

 Found also in Eurasia. Possibly not native in N. A. 



4a. P. lapathifolium L., var. salicifolium Sibth. (See Rhodora 23:259. 1921. 

 P. tomcntosum, var. incanum, of Gray's Man., ed. 7. P. lapathifolium, var. 

 incanum, of Cayuga Fl.) 

 Low gravelly soil near the shores of the larger lakes ; scarce. 

 Renwick (K. M. W. & F. P. Metcalf) ; "borders of Cayuga Marshes, 1858" 

 {Chickering & Brewer in Gray Herb.) ; n. of Cayuga Marshes, 1918. 



Range perhaps the same as for the typical form, of which it may be only a juvenile 

 stage. 



5. P. scabrum Moench. (See Rhodora 23:259. 1921. P. tomentosiim of Gray's 



Man., ed. 7. P. nodosum of Cayuga Fl.) 



Low gravelly or silty soils ; locally abundant. Aug.-Sept. 



Dryden Lake (D. in Gray Herb.); s. end of Cayuga Lake (D.\) ; Myers Point 

 (D.) ; vicinity of Cayuga and on the Cayuga Marshes (D. !) ; abundant in 1919 in 

 the bed of the abandoned canal at Cayuga. 



Newf. to B. C, southw. to N. E. and Calif.; inland, mostly about the Great Lakes. 

 Found also in Eu. Possibly not native in N. A. 



6. P. pennsylvanicum L. 



Moist, rich, open, gravelly or sandy, often alluvial, soils ; rare. Aug.-Sept. 

 Bed of abandoned canal, Cayuga, 1919. 



Coastal regions from N. S. to Miss., and northw. through the Mississippi Basin to 

 s. Ont. and cent. N. Y. 



6a. P. pennsylvanicum L., var. laevigatum Fernald. (See Rhodora 19:70. 1917.) 

 In situations similar to the preceding ; common. Aug.-Sept. 

 N. S. to Ont. and Minn., southw. to Fla. and Tex. 



7. P. amphibium L. 



In shallow calcareous waters of ponds, usually over sandy or gravelly, more rarely 

 mucky, bottoms ; infrequent. July-Aug. 



Spencer Lake, Summit Marsh (/).!), and stations between; Jennings Pond (D. !) ; 

 Dryden Lake (D. !) ; region of Cortland marl ponds; Lake Como ; Junius marl ponds; 

 Cayuga and Montezuma Marshes (D.). 



Newf. to Alaska, southw. to n. N. J., Ky., Colo., and Calif.; rare on the Atlantic 

 Coastal Plain. Found also in Eu. 



The typical aquatic form has floating glabrous subcoriaceous glossy leaves. The 

 terrestrial forms have erect stems and more lanceolate membranous leaves which, 

 together with the stems and sheaths, are strigose-hispid and not glossy. The sheaths 

 may be without a foliaceous border [forma terrestre (Leers) Blake (P. amphibium, 

 var. terrestre Leers, see Rhodora 15:164, 1913)], or with such a border [forma 

 Hartzvricjlitii (Gray) Blake (P. Hartwrightii Gray)]. As has been pointed out by 

 Bissell (Rhodora 4:104. 1902), forma Hartwrightii is in many cases clearly an 

 ecological terrestrial state of P. amphibium, springing from the same rootstocks as 

 would the latter species if the plant were submerged. Whether it is always an 

 ecological form is not certain, though this is probably the case. Forma terrestre has 

 been found at Dryden Lake, Malloryville Bog, and the McLean Bogs; forma 



