NO. 2 drouet: myxophyceae 21 



RIVULARIACEAE 



Calothrix pilosa Harvey ex Bornet & Flahault, Ann. Sci. nat. 

 VII, Bot. 3: 363. 1886. 



Forma trichomatibus 10/x ad 20/ji (ctiam ad 26/y.) crassis; fills 

 10/A ad 40/x crassis. Fig. ly. 



PORTO RICO: On rocks, etc., littoral, M. A. Howe, May 

 1903 (Phyc. Bor.-Amer. No. 1167, in Herb. Missouri Bot. Card.). 

 MEXICO: Rcvilla Gigedo Islands, 'drifted ashore,' Sulphur Bay, 

 Clarion Id., No. 57, January 5. ECUADOR: Galapagos Islands, 

 about the edge of a brackish lagoon near high water level, Albe- 

 marle Point, Isabela Id., No. (/), January 12; about the edges of 

 an inland salt lagoon, Fernandina Id., No. 154, January 14. 



This species, characterized by intercalary heterocysts, attenuate 

 ends of the trichomes, hemispherical terminal cells, and symplocoid 

 habit, was first described and figured by Harvey (Smiths. Contrib. 

 Knowl. 10: 106. 1858) from Key West, Florida. Bornet and Flahault 

 (ibid.), with whose Revision des Nostocacees heterocystees nomen- 

 clature in this group of Myxophyceae begins, cite specimens in 

 European herbaria from Tortola (Leeward Islands), Guadeloupe, 

 the Red Sea, the Friendly Islands, and Mauritius. Geitler (Rabenh. 

 Kryptogamenfl. 14: 612. 1931) cites Dr. Howe's specimen from 

 Porto Rico (Phyc. Bor.-Amer, No. ii6y) as typical of this species. 

 Our material agrees in every respect with this specimen, with the 

 exception in the Mexican material (No. ^y) of the greater breadth 

 of some of the trichomes.'* 



•"'' In the Phycotheca there is a specimen, No. 859 (specimen examined in the 

 Herbarium of the Missouri Botanical Garden), from Point Carmel, Monterey County, 

 California, IV. A. Setchell, June 10, 1901, distributed under the name C. pilosa 

 Harv. I'hc trichomes end in distinct colorless hairs; the heterocysts are basal and 

 often multiseriate; and the mode of branching is usually quite Dicholhrix-like, 

 though scytonemataceous branching is by no means rare. I have not had the op- 

 portunity to examine the type of Dichothrix scriata Sctchell & Gardner (Univ. 

 Calif. Pub. Bot. 6: 473. 1918), but from the description and figures I gather that 

 Phyc. Bor.-Anier. No. 859 might well be placed in that species, 'i he habit of the 

 mass of filaments is reminiscent of Scytonema juliginosa 'I'ilden, American Algae 

 No. 629 (specimen examined in the Herbarium of the Missouri Botanical Garden) 

 from Hawaii, recently redcscribed as the type of the scytonemataceous genus Tildenia 

 Kossinskaja (Not. Syst. Inst. Crypt. Hort. Bot. Princip. U. S. .S. R. 4: 85. 1926); 

 but the absence of colorless terminal hairs in the Hawaiian material prevents our 

 placing Phyc. Bor.-Amer. No. 859 here. Poljansky (Bull. Jard. Bot. Princip. de 

 lU. S. S. R. 1928: 17) places No. 859 in Calothrix dura Harv., a species according 

 to Bornet and Flahault (ibid.) synonymous with C pilosa Harv. The same Russian 

 author transfers C. pilosa Harv. to the genus Tildenia. This latter transfer appears 

 to me unjustifiable, inasmuch as the button-like terminal cells of Phyc. Bor.-Amer. 

 No. 1167 and of our own material appear in rare instances to be true heterocysts. 

 I am indebted to Dr. J. M. Greenman for the privilege of examining the specimens 

 cited above. 



