MIDDLESEX FLORA. 99 



S. minimum, Fries. 

 Ashland (Rev. Thos. Morong). 



NAIADACE>E. PONDWEED FAMILY. 



NAIAS, L. 

 N.flexilis, Rostk. 



Common. 

 N. flexilis, Rostk., var. robusta, Morong. 



Concord River, abundant (Walter Deane) ; Natick (Rev. Thos. 



Morong ; specimen in herb. of). 



" Stem stout, few leaved, sparsely branching, elongated ; leaves 



linear, 1 2mm. broad and 10 15mm. long, flat, abruptly acute. 



I have found it rising to the surface in still ponds, in water 4 to 6 



feet deep." Morong in Bot. Gaz. The usual fruit of the type. 

 N. Indica, Cham., var. gracillima, Braun. 



Woburn (Wm. Boott) ; Spot Pond, Stoneham, and Ashland (Rev. 



Thos. Morong). Rare. 



ZANNICHELLIA, Mich. 

 Z. palustris, L. HORNED PONDWEED. 



Very abundant in Mystic Pond and River (Wm. Boott). June-July. 



ZOSTERA, L. 



Z. marina, L. EEL-GRASS. 

 Very common in salt water. July-Aug. 



RUPPIA, L. 



R. maritima, L. DITCH-GRASS. 

 Common in brackish water. June-July. 



POTAMOGETON, Toum. 



P. natans, L. 



Common. 

 P. Oakesianus, Robbins. 



Mystic Pond, Medford, and Horn Pond, Woburn (Wm. Boott) ; 



Natick (Rev. Thos. Morong). 

 P. Claytonii, Tuck. 



Common. 

 P. Vaseyi, Robbins. 



Mystic Pond, Medford (Wm. Boott) ; Spot Pond, Stoneham (Rev. 



Thos. Morong). 

 P. Spirillus, Tuck. 



Westford (Dr. C. W. Swan) ; Woburn, Winchester, Medford and 



Billerica (Wm. Boott) ; Concord (E. S. Hoar). 



