Myxophyceae 275 



3 Filaments 25-35 mic. in diameter; trichomes 15 mic. in diameter; 



heterocysts oblong, solitary D. penicillata 



4 Filaments 22-30 mic. in diameter; trichomes 7.5-12.5 mic. in diame- 



ter; heterocysts basal and intercalary D. utahensis 



501. Dichothrix montana Tilden. American Algae. Cent. VI. no. 572. 1902. 



De Toni. Syll. Algar. 645. 1907. 



Plant mass expanded, blue-green; filaments 15-25 mic. in diameter; 

 sheaths hyaline; trichomes 5-6 mic. in diameter, sometimes constricted at 

 joints, drawn out into a long hair; cells quadrate or longer than their 

 diameter; heterocysts hemispherical. 



Montana. On rocks in hot water. Lo Lo Hot springs, Lo Lo. September 

 1898. (Griffiths). 



The plant closely resembles D. baueriana, but its filaments are 

 much wider and its habitat quite different. Being very plainly a Dicho- 

 thrix, it cannot be included under Calothrix thermalis, and it 

 is therefore made a new species. 



502. Dichothrix orsiniana (Kuetzing) Bornet and Flahault. Revis. des Nos- 



toc. Ann. Sci. Nat. Bot. VII. 3: 376. 1886. ;De Toni. Syll. Algar. 



5: 641. 1907. 

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

 (Mastigonema orsinianum Kg.); 6: 284. 1879. (S c h. c a t a r a c- 

 tae Naeg.); Fresh-Water Algae U. S. 236. pi. 168. f. i, 2. 1887. (Calo- 

 thrix orsiniana Thur.). Tilden. List of Fresh-Water Algae col- 

 lected in Minnesota during 1895. Minn. Bot. Studies, i: 599. 1896. Col- 

 lins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 9. no. 405. 1898. Col- 

 lins. Phycological Notes of the late Isaac Holden. — II. Rhodora. 7: 238. 

 190S. 



Plate XVIII. fig. 16. 



Plant mass caespitose, made up of penicillate fascicles 2-3 mm. in 

 height, gelatinous, dark green; filaments 10-12 mic. in diameter (in ultimate 

 branches), flexuous, erect, radiating; false branches appressed, enclosed for 

 some distance in a common tegument; sheaths thick, close, soft, uniform, 

 yellow, in lower portions becoming brownish and somewhat opaque; trich- 

 omes 6-7.5 ™ic. in diameter, tapering into a hair; cells shorter than their 

 diameter; cell contents olive green; heterocysts basal. 



Connecticut. Forming gelatinous tufts on rocks at the base of a dam. 

 Pequonnock River, Bridgeport. July 1894. (Holden). New York. On 



rocks in rapids of Niagara River, Niagara Falls. (Wolle). Florida. 



(Wolle). Minnesota. Kenwood, Minneapolis. August 1895. (Tilden). 



503. Dichothrix calcarea Tilden. American Algae. Cent. II. no. 165. 1896. 



De Toni. Syll. Algar. 5: 645. 1907; Some New Species of Minnesota 

 Algae which live in a Calcareous or Silicious Matrix. Bot. Gaz. 

 23: 100. pi. 9. f. 1-3- 1897; List of Fresh-Water Algae collected in 

 Minnesota during 1896 and 1897. Minn. Bot. Studies. 2: 27. 1898. 

 MacMillan. Minnesota Plant Life. 30, 41. f. 8, 10. 1899. 



