Myxophyceae 281 



Farlow. List Marine Algae U. S. Proc. Am. Acad. Arts Sci. 10: 380. 

 1875. Murray. Catalogue of the Marine Algae of the West Indian Re- 



gion. Journ. of Bot. 27: 261. 1889. Collins, Holden and Setchell. Phyc. 

 Bor.-Am. Fasc. 21. no. 1016. 1903. 



Plant mass caespitose, pulvinate, expanded, made up of rigid, fastigiate, 

 twisted tufts 1-3 cm. in height, dichotomously or irregularly branched; com- 

 mon tegument transparent or yellowish; trichomes 5-6 mic. in diameter, 

 tapering into a thin hair at the apex; heterocysts somewhat spherical. 



Florida. On mud flats near high water mark. Key West. (Harvey, 

 Farlow). Forming a turf, i cm. thick, on rocks just below low water mark. 

 Key West. October 1902. (Howe). 



Genus SACCONEMA Borzi. 

 Morfologia, etc. N. Giorn. Bot. Ital. 14: 282, 298. 1882. 



Plant mass or colony small, gelatinous, lobed or torn; common tegu- 

 ment lamellose, very much folded and saccate, finally dissolved at apices, 

 containing from two to many trichomes; trichomes irregularly aggregated, 

 somewhat caespitose; false branches short, moniliform, not coalesced; 

 heterocysts basal, spherical; gonidia present. 



515. Sacconema rupestre Borzi. Note alia Morfologia e Biologia delle 



Alghe Ficocromacee. Nuovo Giorn. Bot. Ital. 14: 282, 298. pi. 16, 

 17. f. 9-12. 1882. Bornet and Flahault. Revis. des Nostoc. Ann. Sci. 

 Nat. Bot. VII. 3: 381. 1886. De Toni. Syll. Algar. 5: 646. 1907. 

 Hauck and Richter. Phyk. Univ. no. 741. 1891. Wittrock, Nordstedt 

 and Lagerheim. Algae Aq. Dulc. Exsicc. no. 1309. 1896. 



Plate XIX. fig. 4. 



Trichomes 8 mic. in diameter; heterocysts basal, spherical; gonidia 15 

 mic. in diameter; wall of gonidium roughened. 



Massachusetts. Suntaug Lake, Tynnfield. September i8go. (Collins). 



Genus ISACTIS Thuret. Essai Class. Nostochinees. 11. 1885. 



Plant mass flat, crustaceous, orbicular, thin, adhering by the lower 

 surface, growing at the margin; filaments parallel, erect, unbranched or 

 rarely sparingly branched; heterocysts basal; gonidia unknown. 



I Filaments decumbent at base; trichomes 7-9 mic. in diameter 



I. plana 



II Filaments slightly swollen at base; trichomes 8-10 mic. in diameter 



I. centrifuga 



516. Isactis plana (Harvey) Thuret. Essai Cla^s. Nostochinees. 11. 1885. 



Bornet and Flahault. Revis. des Nostoc. Ann. Sci. Nat. Bot. VII. 

 4: 344. 1886. De Toni. Syll. Algar. 5: 646. 1907. 

 Wolle. Fresh Water Algae. II. Bull. Torr. Bot. Club. 6: 138. 1877. 

 (M astigonema plana Rab.). Farlow. Marine Algae of New Eng- 



