174 Rhodora [SEPTEMBER 
P. lapathifolium L. Fields, gardens and waste places, common. 
P. lapathifolium L., var. incanum (Willd.) Koch. Stony and 
gravelly shores and wet places; Spot Pond, Stoneham; Winter Pond 
and North Reservoir, Winchester; dump, Boston; flats, South Boston; 
low cultivated ground, Sherborn. 
Specimens from all these places have been carefully examined. 
They have the small achenes of P. lapathifolium L. and should be 
referred to the above variety rather than as a variety to P. tomentosum 
Schrank. 
P. lapathifolium L., var. nodosum (Pers.) Weinmann. Culti- 
vated ground, Sherborn (M. L. Loomis, Aug. 2, 1910 et seq.). 
P. Muhlenbergii (Meisn.) Wats. Muddy places and shallow 
water, occasional. 
P. ORIENTALE L. Garden escape; occasional. 
P. pennsylvanicum L. Moist soil, common throughout. 
P. Persicarta L. Waste places and gardens, very common through- 
out. 
P. prolificum (Small) Robinson. Salt marshes and beaches; 
common along the coast. 
P. ramosissimum Michx. Salt marshes, Watertown (F. S. 
Collins, July 28, 1886); waif in dry sand by railway, Belmont (C. H. 
Knowlton, Aug. 26, 1911). 
P. ramosissimum Michx., f. atlanticum Robinson. Medford, 
Cambridge, Watertown, Dorchester, Scituate. A peculiar form from 
Oak Island, Revere, somewhat resembling P. erectum probably be- 
longs here. 
P. rurtvacum Jord. Watertown (C. E. Perkins, Aug. 25, 1881). 
An Old World species. 
P. sagittatum L. Low grounds, very common and abundant 
throughout. 
- P. scandens L. Swamps and wet thickets, common. 
. P. tenue Michx. Dry rocky and sandy places, frequent. 
P. virginianum L. Moist shady places; Lexington; Beaver 
Brook Reservation, Belmont; Stony Brook Heservation in W. 
Roxbury and Hyde Park. 
RHEUM. 
R. RuaroNTiCcUM L. Open field, Beaver Brook Reservation, Bel- 
mont (W. Deane, Apr. 25, 1896). Frequently persistent after culti- 
vation, but seldom collected. Originally from southern Siberia. 
