MIDDLESEX FLORA. 37 



M. tenellum, Bigel. 

 Cambridge and Tewksbury (Bigelow's Fl. Bost.) ; Natick (Austin 

 Bacon) ; Silver Lalie and Mystic Pond (Wm. Boott) ; Groton and 

 Westford (Dr. C. W. Swan). July-Aug. 



Proserpinaca, L. 



P. palustris, L. Merjeaid Weed. 

 Common. June-July. 



Trapa, L. 



T. NATANS, L. Water Chestnut. 



Medford and Maiden (F. S. Collins) ; Concord River (C. W. Jenks). 

 Introduced from Europe, and, in tlie last locality, apparently 

 naturalized. 



" Eootstock furnished at the joints with tufts of roots, each tuft 

 forming a pyramidal plume; leaves floating, abont 1^ in. broad, 

 rhomboidal, thickish and nerved, bimucronately toothed, subpub- 

 escent at the nerves beneath ; petiole 2-3 times longer, distended 

 below blade into an oblong intumescence, filled with cellular pith, 

 and acting as a buoy ; flowers small, white, submersed, pellucid ; 

 peduncles 1-flowered, axillary." Bot. Reg., Vol. 1. 



ONAGRACE/E. EVENING- PRIMROSE FAMILY. 



CiRC^A, Tourn. 

 C. Lutetiana, L. Enchanter's Nightshade. 



Common. June-July. 

 C. alpina, L. 



Generally distributed, but not so common as the preceding. July. 



Epilobium, L. 



E. angustifolium, L. (E. spicatum, Lam.) Great Willow- 

 Herb. 

 Very common. July-Aug. 



E. palustre, L., var. lineare, Gray. 

 Common. Aug.-Sept. 



E. coloratum, Muhl. 

 Common. July-Sept. 



CEnothera, L. 



CE. biennis, L. Evening Primrose. 

 Very common. June-Sept. 



CE. biennis, L., var. muricata, Lindl. 

 Cambridge (F. S. Collins). 



