Ulothrix 151 



Hormiscia oscillarina DeToni, Syll. Alg. I : 167. 1 



Cells about 11 p. in diameter, and %— J /i as long, or equal to 

 the diameter in length ; chromatophore a broad band. 



Exsic: Phyc. Bor. Am. 61 3, Melrose, Mass., Aug. 1890, 

 floating in a ditch (F. S. Collins). 



When we visited this station in May, 1901, with Mr. Collins, no 

 Ulothrix was to be seen ; possibly this is unlike most species of 

 this genus in being a summer form. 



A specimen labelled U. oscillarina from Wisconsin in the 

 Wolle herbarium is Tribonema sp. 



In regard to the name of this species, it is probable that 

 Agardh's form ought to be used. The specimen issued as Con- 

 ferva oscillatorioides Ag. (Desmaz. PI. Crypt, de France, iJSj) 

 agrees closely with Mr. Collins' plant ; but as we have no means 

 of determining with certainty the character of Agardh's plant, 

 Kiitzing's name is here retained, as being the one in current use. 



5. Ulothrix tenerrima (Kiitz.) Kiitz. Phyc. Gen. 253. pi. p.f 1. 

 1843 ; Phyc. Germ. 197. 1845 \ Spec. Alg. 346. 1849 

 (Excl. var.); Tab. Phyc. 2: pi. 87. f 1. 1852. Rabenh. 

 Krypt. Flor. Sachs. 1 : 264. 1863 ; Flor. Eur. Alg. 3: 366. 

 1868. Gay, Rech. sur Alg. Vert.//. 12. f. ng. 1891. 

 Conferva tenerrima Kiitz. Linnaea, 8: 346, 347, 361. p. p. 



1833- " 



Myxonema f tenerrimum Rabenh. Deutsch. Krypt. Flor. 2 2 : 

 99. 1847. 



Ulothrix subtilis tenerrima Kirchner, Krypt. Flor. Schles. 

 2 1 : 77. 1878. Wolle, F. W. Alg. 136. //. 118. f 17. 1887. 



Hormiscia subtilis tenerrima DeToni, Syll. Alg. 1 : 160. 1889. 



Ulothrix tenuis Kiitz. Spec. Alg. 346. 1849. (?) 



Filaments forming light green silky or floccose masses often 1 

 dm. long ; cells cylindrical, 7.5-9// in diameter, %-l}4, times as 

 long ; cell-wall very thin ; chromatophore zonate or contracted to 

 one side of the cell, with one pyrenoid (pi. 21. f. 3, f). 



On the sides of an iron fountain basin, and in a wooden water- 

 ing-trough, St. Johnsbury, Vermont, September and October 

 (645, 651). 



The chromatophore in the actively vegetative state is zonate, 

 and the appearance of a filament is then like a miniature specimen 



