1921] Fernald, — Expedition to Nova Scotia 191 



foundland collections are sparingly fruiting, while the Nova Scotia 

 plant is sterile, but exactly similar material from the Magdalen Is- 

 lands as well as from southern Maine has good fruit which is quite 

 like that of var. graminifolius. In fact, a large series of specimens of 

 var. spafhulaeformis (from Newfoundland, Anticosti Island, the Mag- 

 dalen Islands, Nova Scotia, Maine, Massachusetts and Connecticut) 

 seems to be separable from var. graminifolius only by its round- 

 tipped or decidedly obtuse submersed leaves. It has been generally 

 surmised that P. spathaeformis or P. variant is a hybrid of P. grant- 

 incus or its var. graminifolius with P. angustifolius Berchtold & Presl; 

 but since the latter species is unknown northeast of Massachusetts, 

 while the supposed hybrid extends as a fertile plant to eastern New- 

 foundland, its hybrid nature is certainly extremely doubtful. Fur- 

 thermore, the fertile obtuse-leaved plant of Newfoundland, the Mag- 

 dalen Islands and Maine has the characteristic small fruit of P. 

 gramineus and its var. graminifolius. 



P. bupleuroides Fernald. Frequent in brackish waters. Rare 

 in fresh water: seen only in Midway (Centreville) Lake, Centreville, 

 Digby Co. See p. 163. 



The characters originally pointed out seem consistently to dis- 

 tinguish P. bupleuroides from the European and northern P. per- 

 foliatus L. — the less puckered leaf, fewer nerves, slender stem, 

 almost filiform peduncle without much spongy thickening, and 

 smaller, firm and olive-brown fruit. Dr. St. John and I have re- 

 viewed the material and find no specimens to match old world P. 

 perfoliafus from south of Labrador. 



* P. Friesii Rupr. Seen only in Colchester and Cumberland 

 Cos.: quiet waters of Salmon River, Truro; spring-pools and ditches 

 south of Amherst. 



* P. confervoides Reiehenb. Deep or shallow water of lakes, 

 small ponds and bog-pools, frequent in Yarmouth Co.: deep water 

 of Trefry's Lake, Arcadia; peaty and muddy pond-hole near head 

 of St. John Lake, Springhaven; water-holes in sphagnous bog by the 

 station, Argyle; drifted ashore from deep water of Great Pubnieo 

 Lake. See pp. 145, 149. 



* P. dimorphus Raf. Shallow water on tidal flats of Tusket 

 River, Tusket Falls, Yarmouth Co. 



* P. FILIFORMIS, var. borealis (Raf.) St. John, Rhodora, xviii. 

 KM (1916). Fresh to brackish swale at head of Baddeck Bay, Pad- 

 deck. 



* P. vaoinatus Turez. Bull. Soc. Nat. Moscou, xi. 102 (1838); 

 St. John, Rhodora, xx. 191 (191 S). P. moniliformis St. John, 



