116 Rhodora [May 



LUDVIGIA. 



L. alternifolia L. Moist soil, occasional. 



L. palustris (L.) Ell. Ditches and wet ground, common through- 

 out. 



L. polycarpa Short & Peter. Wet shores of Round and Winter 

 Ponds, Winchester (Win. Boott, October, 1885; many other collec- 

 tions to date). 



L. sphaerocarpa Ell. Marshes along Concord River; also Wal- 

 tham (C. E. Perkins, Aug. 4, 1881). 



OENOTHERA. 



0. biennis L. Rich soil and waste places, common. 



O. bistorta Nutt. Wool-waste, N. Chelmsford (If. P. Alcott, 

 June 23, 1879). Specimen in herb. N. *'. Botanical Club. A Cali- 

 fornian plant. 



O. grandiflora Ait. Escaped or persistent in Essex County 

 and at Maiden, Lexington and Dorchester. 



0. hybrida Michx., var. ambigua Nutt. (0. fraticosa L.) See 

 Rhodora xx. 51-52, 1918. Single specimens have been reported 

 from Beverly and Eramingham; Cambridge (E. Tuckerman, Jr., no 

 date.). 



O. LACINIATA Hill. An occasional weed, spontaneous from further 

 west. 



O. Oakesiana Bobbins. Cohasset (A. T. Kidder, July 21, 1880). 

 Specimen in herb. Gray. 



0. muricata L. Sandy soils and waste places, common and variable. 



O. cruciata Nutt. Dry soil, rare; Rockport, Wenham, Chelms- 

 ford, Woburn, Lincoln. 



O. pratensis (Small) Robinson. Dry soil, rare (K. R. Farrar, — 

 1891); Needham (T. 0. Fuller, June 23, 1889); Walpole (C. II . 

 Knowlton, June 27, 1909). 



O. pumila L. Fields, very common throughout. 



HTDROCARYACEAE. 

 TRAP A. 



T. natans L. In Concord and Sudbury Rivers at Concord and 

 Bedford, introduced by Minot Pratt; Eresh Pond, Cambridge 

 (Thomas Morong, Aug. 11, 1879); Belmont (C. E. Perkins, Septem- 

 ber, 1882); reported at Maiden and Medford according to Dame & 

 Collins, Fl. Middlesex Co., 37, 1888. 



