158 MIDDLESEX FLORA. 



somewhat as if arranged in irregular longitudinal lines, the lower 

 elongate, the upper gradually shorter, when mature roundish and 

 not in lines." J. G. Agardh, Till Algern. Syst. IV., 109. 

 M. latissimum, Wittr. 

 Medford, claypits, etc. Common in summer in somewhat brackish 

 water. Not before reported from America. 



"Frond delicate, of irregular outline, 1-3 dm. in diameter, much 

 plicate, with entire or undulate margin, lubricous, bright green, in 

 the upper part .02 to .026 m m. thick ; cells seen from the sm-face, 

 without definite arrangement, rather closely set, irregularly 4 or 6 

 angled, with somewhat rounded corners; in ci"oss section of the 

 frond oval or almost circular, .014 to .018 mm. long." F. Hauck, 

 Meeresalgen Deutschlands. 



PROTOCOCCACE/E. 



Vol vox, Ehren. 



V. globator, Ehren. 

 Maiden, pond in Middlesex Fells (R. Frohock). 



Pediastrum, Meyer. 



P. Ehrenbergii, A. Br. 

 Holliston, on walls of B. & A. R. R. tunnel. 



Ophiocytium, Naeg. 



O. cochleare, A. Br. 

 Hudson. 



Protococcus, Ag. 



p. vlridis, Ag. 

 Very common everywhere. 



Tetraspora, Ag. 

 T. bullosa, Ag. 



Maiden. 

 T. lubrica, Ag. 



Maiden, et al. ; common in spring. 



PORPHYRIDIUM, NaSg. 



p. cruentum, Naeg. 

 Medford. 



Glceocystis, iSTaeg. 



G. Paroliniana, Naeg. 

 Newton (W. G. Farlow). 



