28 Rhodora [FEBRUARY 
A. J. Eames & C. H. Knowlton, Sept. 6, 1909; M. L. Fernald, Sept. 10, 
1909; K. M. Wiegand, Sept. 21, 1909); Lake Cochituate, Natick 
(K. M. Wiegand, Oct. 1, 1909. See Rnopona, xii, 39, 1910). 
C. dentatus Torr. Wet shores and marshes, abundant throughout. 
C. dentatus Torr., var. ctenostachys Fernald. Plum Island, 
Essex Co., with type and intermediates (J. Robinson, Aug. 26, 
1878); “along the gravelly pond shores below spring level, not rare,” 
Houghton’s Pond, Milton (4. W. Cheever, Aug. 18, 1905). 
C. diandrus Torr. Low ground, in sand, gravel or mud. Not 
reported from the three southern tiers of towns; abundant in the rest 
of the district. Collected in Sudbury meadows by Francis Boott 
in 1819, and at Danvers by B. D. Greene in 1846. 
C. Engelmanni Steud. Borders of ponds. Fresh Pond, Cam- 
bridge (Wm. Boott, Aug. 20, 1853. Since then collected by various 
others down to 1908); Spy Pond, Arlington (H. A. Young, Sept. 21, 
1879; C. E. Perkins, September, 1881); Little Pond, Belmont (H. A. 
Young, Sept. 21, 1879); Framingham (T. Morong, September, 1886; 
A. J. Eames & C. H. Knowlton, Sept. 6, 1909; abundant, Farm 
Pond, K. M. Wiegand, October 9, 1909). 
C. erythrorhizos Muhl. Wet sandy and muddy shores. New- 
buryport (A. A. Eaton, Oct. 3, 1896); Lawrence (J. Robinson, Sept. 
26, 1877. Various other collectors down to 1901); Winter Pond, 
Winchester (H. H. Bartlett, J. R. Churchill & C. H. Knowlton, 
Sept. 15, 1906). 
C. esculentus L. Moist soil and cultivated ground. Amesbury, 
West Newbury, Lawrence, South Boston, Concord, Wayland, Fram- 
ingham; Danvers (according to Robinson, Fl. Essex Co. 115, 1880); 
Lowell, Tewksbury and Dracut (according to Dame & Collins, Fl. 
Middlesex Co. 111, 1888). 
C. ferax Richard. Low ground and marshes, near fresh or brackish 
water. Scattered stations in eastern portion of district; known in the 
Fenway, Boston, from September, 1878, to the present. 
C. filiculmis Vahl. Dry sterile soil; Malden, Woburn, Win- 
chester, Cambridge, Charlestown, Boston, Quincy, Hull, Sharon, 
Norfolk, Wellesley. 
C. filiculmis Vahl, var. macilentus Fernald. Very common 
throughout. 
C. ruscus L. "Near Revere beach, 1877 (Herbert A. Young)" 
according to Robinson, Fl. Essex Co. 116, 1880). It was also col- 
