152 MIDDLESEX FLORA. 



The following list includes both fresh and salt water species ; as to 

 the latter, it is believed to be reasonably complete for the very 

 limited "coastline" of Middlesex county. There is no rocky shore 

 or sandy beach, but only a salt marsh with muddy banks, extending 

 two or three miles up the Charles and Mystic rivers, so that only a 

 very limited marine flora is to be expected. Not uncommonly plants 

 of Laminaria, etc., are left by the tide within our limits, but as they 

 are undoubtedly brought from a distance, they are not included here. 



As regards fresh water algae, those species are given which are 

 known to have been found in the county, but they are only a small 

 portion of what would be obtained by a careful observer who could 

 give sufficient time to the study ; such genera as Spirogyra, Conferva, 

 Scytonema, and Oedogonium, barely or not at all represented here, 

 are abundantly found in the county; so are also Desmids and 

 Diatoms, which have been entirely omitted here, except that a list of 

 the former has been included, taken from the paper by G. Lagerheim, 

 "Bidrag till Amerika's Desmidie-Flora." The species in question 

 were obtained by Lagerheim from specimens of Utricularia, col- 

 lected at Tewksbury by B. D. Greene, and preserved in Swedish 

 herbaria. 



The fresh and the salt water algae are not given in separate lists, but 

 the marine and submarine species are designated as such. Where 

 not otherwise stated, the authority for a locality is F. S. Collins; 

 and all species are represented by specimens in the Middlesex Insti- 

 tute herbarium, except those credited to Prof. W. G. Farlow, which 

 are represented by specimens in his herbarium ; for Prof. Farlow's 

 kindness in giving access to his very rich collection, and for his 

 assistance in many difficult questions of determination^ the authors 

 are greatly indebted. 



FLORIDEv^E. RED ALGSE. 



POLYSIPHONIA, Grev. 



P. nigrescens, Grev. 

 Medford, in a ditch in the salt marsh. Rare. 



GELIDIUM, Lamour. 



G. crinale, Ag. 



Medford, on stones, etc., in the Mystic river, between tide marks. 

 Inconspicuous and easily overlooked, but not uncommon. 



