1915] Flora of the Boston District,—— XX. 173 
P. aviculare L., var. littorale (Link) Koch. Edge of salt marshes; 
Revere, Chelsea, South Boston, Scituate and probably elsewhere on 
the coast. 
P. aviculare L., var. vegetum Ledeb. Oak Island, Revere ( H. A. 
Young, Aug. 3, 1882; G. G. Kennedy, Aug. 6, 1894); Boston (C. E. 
Perkins, June 12, 1879); chicken-yard, Sherborn (M. L. Loomis, 
July 15, 1912, July 25, 1913). 
P. BELLARDI All. S. Boston (E. & C. E. Faxon, July 3, 1879). 
Adventive from western Asia or eastern Europe. 
P. Bistorta L. Garden escape, Boxford (Rev. W. P. Alcott, June 
13, 1890); weed in garden, Malden (W. H. Manning, —, 1883; Mrs. 
N. M. Hunnewell, May 31, 1886). A boreal species, native of Eu- 
rasia and western North America. 
P. Careyi Olney. Swamps and moist places, frequent. No reports 
from Plymouth County. 
P. cilinode Michx. Dry ledges and clearings; occasional, espe- 
cially on Cape Ann. 
P. Convotvutus L. Gardens and waste places; common. 
P. cuspipatum Sieb. & Zucc. Waste places; recently introduced, 
and especially frequent in Boston and immediate vicinity; also at. 
Danvers, Wakefield, and Lexington. 
P. dumetorum L. Rich soil; reported from only eight stations, 
but probably much more common than this would indicate. 
P. dumetorum L., f. cristatum (Engelm. & Gray) Robinson. 
Blue Hills, W. Quincy, common (J. R. Churchill, Aug. 29, 1891). 
P.erectum L. Fields and waste places; occasional in central and 
northern towns. 
P. exsertum Small. Brackish meadows and salt marshes; Ips- 
wich, Cambridge, Boston, Brighton. 
P. glaucum Nutt. (See RuopoRA xv. 68-73, 1913.) Revere 
(C. E. Faxon, no date; the specimen is in the Gray Herbarium). 
The specimens quoted by John Robinson, Fl. Essex Co. 92, 1880 as £ 
maritimum L. although some are immature, seem to be P. proli- 
ficum (Small) Robinson. 
P. Hydropiper L. Moist soil, very common throughout. 
P. hydropiperoides Michx. Brooks and swamps; common 
throughout. 
P. hydropiperoides Michx., var. strigosum Small. Wayland, 
Wellesley, Dedham, Milton, Canton. 
