32 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



BEGGIATOA, Trevisan. 



(Named in honor of Francesco Sccondo Bcggiato, an Italian botanist.) 



Filaments simple, hyaline, no proper sheath, rapidly oscillating, 

 cells filled with opaque granules. Spores unknown. 



A genus separated, from Oscillaria only by its color, which is white to the naked 

 eye, and by the granules of sulphur which often make the cell seem quite opaque 

 when viewed with the microscope. The species give off a strong odor of hydric sul- 

 phate, and are found in both fresh and salt water, especially in hot springs. The 

 diameter of the filaments, an uncertain mark, is about the only guide to the distinc- 

 tion of the species. 



B. alba, Treves, var. marina (Warming, Videnskab. Middels., 1875, 

 PL X, Figs. 0, 7). 



Filaments .003G mm in diameter, cell divisions indistinct, granules 

 usually irregularly placed. 



Cambridge ; Europe. 



In brackish ditches. 



B. arachnoidea, Bab. (Warming, 1. c, PI. X, Figs. 2-4). 



Filaments .005-7 mm in diameter, cells narrower than broad, granules 

 usually in bands parallel to the transverse cell-walls. 



Eastport, Maine ; Wood's Holl, Mass. ; Europe. 



On dead algse. 



B. mirabilis, Cohn (Warming, 1. c, PI. X, Fig. 5). 



Filaments .OIC 111111 (20-40, Warming) in diameter, cells a third as long 

 as broad, granules arranged in bands. 



Cambridge, Mass. ; Europe. 



There is a doubt about the accuracy of the determination of the specimensreferred 

 to this species. It is much the largest of the genns found on our coast. The only 

 specimens which we have measured were .016 mm in breadth, which agrees with the 

 measurement of Cohn, but not with that of Warming. We have the impression, 

 however, that we have seen larger specimens than those measured. 



Leptothrix rigidula, Kiitz., is found at Wood's Holl, on Ectocarpus and other algse. 

 The genus Leptothrix is now limited to small species related to Bacillus. The pres- 

 ent species is parasitic on Ectocarpus and Cladophora, on which it forms white fringes 

 in midsummer. The filaments are about .002 Inm in diameter. The cell divisions are 

 very indistinct. The species may possibly be the same as Beggiaioa minima, Warm- 

 ing, 1. c, PI. X, Fig. 10. 



OSCILLABIA, Kiitz. 



(From oscillo, to vibrate.) 



Filaments simple, destitute of distinct sheath, oscillating, bluish 

 green or dark purple. 



The species of this genus are found on mud, wharves, and wood work. They are 

 not usually fouud pure, but mixed with Spirulina, Lyngbya, &c. The following are 

 all to which we care to give a name, but not by any means all which occur with us. 



