MIDDLESEX FLORA. 37 



M. tenellum, Bigel. 



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

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

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



PROSERPINACA, L. 



P. palustris, L. MERMAID 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 the last locality, apparently 

 naturalized. 



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

 forming a pyramidal plume; leaves floating, about 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. 



, 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). 



