86 University of Calif arnia Puhlications in Botany V'^ou 8 



rules of the Bnissels Congress, and the existence of the earlier Vagin- 

 aria, according to the American Code. Otto Kuntze (1891, p. 926) 

 has stated the case for the retention of Vagijiaria. 



Microcoleus contains between twenty and twenty-five species and 

 is, for the most part, readily recognizable. The species are to be 

 distinguished from those of Sirococoleum rather by habit than by any. 

 other character, while from Hydrocoleuni they differ in the larger 

 number of usually smaller trichomes in a sheath. There are species, 

 however, and Microcoleus cojifluens S. and G. is one of them, which 

 seem to be intermediate between the two genera. 



Key to the Species. 



1. Cells longer than broad 2 



1. Cells shorter than broad 3 



2. Trichomes 2 5-6/i. thick 1. M. chthonoplastes (p 86) 



2. Trichomes 1.5-2At thick 2. M. tenerrimus (p 87) 



3. Trichomes 7-8/i thick, apical cell acute conical 3. M. Weeksii (p 87) 



3. Trichomes 4.4-5/u. thick, apical cell rounded 4. M. confluens (p 88) 



]. Microcoleus chthonoplastes (]\Iert.) Thuret 



Filaments forming dense, thick, coriaceous, extensive layers on 

 damp mud or inundated ground, or at times intermingled with other 

 species of algae, dark olive green ; sheaths cylindrical, tapering at both 

 ends, sometimes completely closed, or open and the trichomes project- 

 ing ; trichomes blue-green, short, nearly straight, numerous, and closely 

 packed within the sheath, constricted at the joints, 2.5-6/a diam., cells 

 3.6-10/A long; apices attenuate, acute, conical. 



Growing on mud in salt marshes. Common along the coast from 

 Puget Sound, Washington to Southern California. 



Thuret, Essai Class. Nost., 1875, p. 378 ; Setchell and Gardner, Alg. 

 N.W. Amer., 1903, p. 188 ; Collins, Holden and Setchell, Phyc. Bor.- 

 Amer. (Exsicc), no. 906; Gomont, Monogr. des Oscill., 1892. p. 353, 

 pi. 14, figs. 5-8 (1893, p. 91, Repr.). Conferva chthonplastes Mertens^ 

 in Hornemann, Fl. Dan., 1813, vol. 9, fasc. 25, p. 6, pi. 1845. 



This widespread species was found first "in sinu Othiniensi" in 

 Denmark by Hofman Bang and described by Mertens in 1813. It is 

 usually found in shallow pools in salt marshes and prefers the waters 

 or moist mud warmed by the sun, whence it may readily be distributed 

 through the agency of water birds in the mud adhering to their feet. 

 Our specimens seem clearly of this species. 



