MIDDLESEX FLORA. 157 



Ulothrix, Thuret. 



U. f lacca, Thuret. 



Salt marshes, abundant. 

 U. subtilis, Kuetz. 

 Newton (W. G. Farlow) ; and elsewhere. 



Conferva, Link. 



C. f loccosa, Ag. 



Common in fresli water. 

 C. globulosa, Kuetz. 

 Cambridge brick yards (W. G. Farlow). 



Ulva, (L.) Le Jolis. 



U. Lactuca, (L.) Le Jolis. 



Very common in salt and brackish water. 

 U. enteromorpha, Le Jolis, var. compresssa, Le Jolis. 

 U. enteronsjorpha, Le Jolis, var. intestinalis, Le Jolis. 

 U. enteromorpha, Le Jolis, var. lanceolata, Le Jolis. 



The first two varieties very common, and the last not uncommon, 



in salt and brackish water ; all varying much in size and form. 

 U. c lath rata, Ag. 



Common in salt water, though not so abundant as the preceding 



species. Quite variable, including among other forms the var. 



Rothiana, forma prostrata, Le Jolis, at Medford. 

 U. Hopkirkii, Harv. 



Medford salt marshes. 



MONOSTROMA, Wittr. 



M. Grevlllei, LeJolis. 

 Mystic river, on pebbles, etc. , between tide marks, in early spring. 



M. Vahlii, Ag.? 

 Ditch in Mystic river salt marsh, Medford. The determination is 

 not absolute, as Prof. J. G. Agardh, to whom specimens were sub- 

 mitted, says : " Your plant comes very near to, or is quite the same 

 as a plant from Greenland, which I have described as M. Vahlii." 

 It does not appear to have been found since the original discovery, 

 unless this is the same species. In this locality it begins to grow 

 quite earlj' in the spring, the fronds being of considerable size when 

 the ice breaks up, which is usually early in March; and by the 

 middle of April it has entirely disappeared. 



" Fi'ond rather large, cylindric-obovate, tubular, noticeably dilated 

 from the slender stipe, entire, or the apex finally ruptured ; mem- 

 brane delicate, collapsing, the cells somewhat clathrate in arrange- 

 ment, the younger angular, separated by thickish walls, appearing 



