MlCROTHAMNION 191 



i. Microthamnion Kuetzingianum Nageli ; Kiitz. Spec. Alg. 

 352. 1849 ; Tab. Phyc. 3 : pi. 1. 1853. DeToni, Syll. Alg. 1 : 

 256. 1889. Kirchn. Mik. Pflanz. //. /. / 10. 1891. De 

 Wild. Flor. Alg. Belg. ^- /• r 3- 1896. (?) Schmidle, 

 Hedwigia, 38: 169. pi. 7. /. 13-15. 1899. Chodat, Beitr. 

 Krypt. Flor. Schweiz. I 3 : 288. /. 202, 203. 1902. (?) 

 Scarcely Wolle, F. W. Alg. pi. 105. f. 1-4. 188;. 

 Mature plants 60-200 ft tall, very densely and irregularly 

 branched from the base, the main trunk soon disappearing in the 

 ramifications ; branchlets one- to several-celled, divergent, some- 

 times curved, not narrowed at the ends ; cells cylindrical or some- 

 times subclavate, 3-4 // in diameter, 2-4 (rarely 5-8) times as 

 long ; chromatophore bright green, covering nearly all the outer 

 cell-wall {pi. 26,/. 1 ; pi. 2j,f. 2-4). 



Exsic. : Phyc. Bor. Am. 568. Greenhouse, Cambridge, 

 Mass., 1899. (F. S. Collins). 



Plants solitary or more often forming a thin bushy coating on 

 small dead stems, etc. In watering troughs, in rivulets, and on 

 dripping rocks. 



Connecticut: Watertown, May, (561 B). 



New York: Morningside Park, March to June (322, 352, 



424, 532). 



Chodat's description of the chromatophore as covering only two 

 thirds of the circumference of the cell wall, as. well as the open char- 

 acter of the branching in his figures do not agree with what is here 

 (and by Schmidle also) considered the typical form of this species. 



2. Microthamnion strictissimum Rabenh. Alg. Sachs. 829. 



1859; Krypt. Flor. Sachs. I: 236 (fig.), 266. 1863; Flor. 



Eur. Alg. 3: 375. 1868. Schmidle, Hedwigia, 38: 169. pi. 



j.f. 4, 5. 1899. 



Microthamnion Kuetzingianum strictissimum Hansg. Prod. Alg. 

 B6hm. 1: 91. 1886. DeToni, Syll. Alg. 1: 258. 1889. Cho- 

 dat, Beitr. Krypt Flor. Schweiz, I 3 : 288. 1902. 



Mature plants 300-600 fi tall, erect, branches generally alter- 

 nate, the main trunks distinguishable even to the summit ; branch- 

 lets erect or ascending, obtuse and not narrowed at the apex ; cells 

 cylindrical, 2.5-4 ft in diameter, 3-12 or even 15—20 times as long ; 

 chromatophore thin, pale green, not always encircling the cell 

 (pi. 26, f. 2- 5 ). 



