100 MIDDLESEX FLOEA. 



P. hybridus, Michx. 

 Winchester; Silver Lake, Wilmington; and Round Pond, Woburu 

 (Wm. Boott) ; Bedford (Dr. C. W. Swan) ; Medford, clay-pits (F. 

 S. Collins). 



P. lonchites, Tuck. 

 Wiucliester (Rev. Thos. Morong). 



P. pulcher, Tuck. 

 Spot Pond, Stoneham, and Ashland (Rev. Thos. Morong) ; Fresh 

 Pond, Cambridge (E. Tuckerman) ; Concord (Walter Deane). 



P. amplifolius, Tuck. 



Mystic Pond, Medford (Wm. Boott) ; Fresh Pond, Cambridge 

 (Rev. Thos. Morong) ; Concord (Walter Deane) ; Townsend and 

 Bedford (Dr. C. W. Swan). 



P. gramineus, L. 

 Common. 



P. gramineus, L., var. spathulaeformis, Robbins. 

 Mystic Pond (Rev. Thos. Morong). 



P. gramineus, L., var. maxim us, Morong. 

 So. Natick (Rev. Thos. Morong). 



"This variety generally occurs in swift cm-rents, and differs from 

 the type in usually having all the parts much elongated, stems 5 to 

 10 ft. ill length, and the sessile or petioLue submerged leaves 3-7 

 lines wide by 2-5 inches long, and 7-10 nerved." Morong in litt. 



P. lucens, L. 



Fresh Pond (Rev. Thos. Morongj ; Winchester (L. L. Dame). 



P. Zlzii, Mert. & Koch. (P. lucens, L., var. minor, Nolte, Man.) 

 Fresh Pond (Rev. Thos. Morong). 



P. praelongus, Wulf. 

 Fresh Pond (John Robinson, et al.) 



P. perfoliatus, L. 

 Mystic Pond (Wm. Boott) ; Fresh Pond (Dr. C. W. Swan). 



P. Mysticus, Morong. 

 Mystic Pond, Medford (Rev. Thos. Morong). 



"The whole plant very slender; stems irregular) j^ branching from 

 a creeping rootstock, nearly filiform, terete, 1-3 ft. high ; leaves all 

 submerged, scattered, entire, oblong-linear, ^a-l)^ inches long, and 

 2 or 3 lines wide, 5-7 nerved, finely undulate, obtuse or bluntly 

 pointed at the apex, abruptly narrowing :it the base, and sessile or 

 partly clasping; stipules fi-ee, obtuse, about 6 lines long, mostly 

 deciduous but often persistent, and closely sheathing tlie stem; 

 spikes few, capitate, 4-6 flowered, on erect peduncles from 1-2 inches 

 long. With the habit of P. perfoliatus, but scarcely % as stout in 

 any of its parts." Morong in Bot. Gaz., Vol. V., No. 5. 



