272 Minnesota Algae 



Plant mass caespitose; filaments up to 14 mic. in diameter, elongate, 

 flexuously curved, not branched, truncate at the apex; sheaths moderately- 

 close, firm, thick, colorless, with truncate and open apex; trichomes often 

 interrupted; cells three to five times as long as their diameter; transverse 

 walls sometimes distinct, sometimes inconspicuous; heterocysts spherical or 

 compressed, about as wide as the trichome; gonidia up to 4 mic. in diame- 

 ter, cylindrical, often many in series in one filament; cell contents green. 



Pennsylvania. In a stagnant pool in "Bear Meadows," forming a fila- 

 mentous, felty mass with other algae. Allegheny Mountains, Centre County. 

 (Wood). 



493. Mastigonema fibrosum (Wood) Wolle. Fresh-Water Algae U. S. 244. 



pi. 174. f. 8. 1887. Wood. Contr. Hist. Fresh-Water Algae North 

 America. 54. pi. S- f- 3- 1827. De Toni. Syll. Algar. 5: 631. 1907. 

 Plant mass light bluish green or olive; filaments lo-ii mic. in 

 diameter, with apex prolonged into a long, hyaline hair; sheaths trans- 

 parent, in the immature filament distally broad and distinct, although 

 hyaline, below rather thick and close, in the mature filament below close, 

 indistinct, above dissolved in fibrillae and wanting at the apex; trans- 

 verse walls distinct; heterocysts spherical, sometimes in pairs. 



Pennsylvania. In a thick jelly, with other algae, on wet dripping rocks. 

 Near Manayunk. (Wood). 



494. Mastigonema halos Wood. Contr. Hist. Fresh-Water Algae North 



America. 52. pi. 5. f. 2. 1872. De Toni. Syll. Algar. 5: 630. 1907. 



Plant mass caespitose; filaments up to 12 mic. in diameter, unbranched, 

 in mature state greatly elongate and with the sheath truncate and open, 

 in the young condition shorter and often ending in a rather short hair; 

 .<;heaths firm, rather thick, often distinctly lamellose, colorless; trichomes 

 7 mic. in diameter, continuous or interrupted; cells short; heterocysts 

 somewhat spherical; cell contents finely granular. 



Connecticut. Growing in little tufts in salt or brackish water. Stoning- 

 ton Inlet. (Wood). 



495. Calothrix lacucola Wolle. Fresh Water Algae. V. Bull. Torr. Hot. 



Club. 8: 39. 1881; Fresh-Water Algae U. S. 239. pi. 172. f. i. 1887. 

 Wolle and Martindale. Algae. Britton's Catalogue of Plants found 

 in New Jersey. Geol. Surv. N. J. 2: 603. 1889. De Toni. Syll. Al- 

 gar. S: 629. 1907. 



Plate XVIII. fig. 13. 



Plant mass floating, dull yellow or brownish; filaments 15-20 mic. in 

 diameter at the base, very much branched; false branches somewhat spread- 

 ing, not concrete, moderately tapering, with obtuse, slightly bent apices, 

 elongate, interwoven; sheaths close, colorless or yellowish; trichomes thin, 

 homogeneous or with distinct transverse walls; cells equal to or two or 

 three times shorter than their diameter; heterocysts spherical, usually single 

 at the base of the branches, equalling the trichome in diameter. 



Nevir Jersey. Split Rock Pond, Morris. (Wolle). 



