488 University of California Piiblications in Botany [Vol. 6 



Ulothrix pseudoflacca f. maxima Setchell et Gardner forma nov. 



Plate 42, fig. 6 



Filis brevibus, plus miniisve contortis, hibrieis, atroviridibus, 

 16-36/A, viilgo 28-32/x diam. ; cellulis brevibus, 4-8/t longis ; parietibus 

 cellularum 4-5/a crassis, horaogeneis hyalinisque ; chromatophoris in- 

 complete annulatis parietes externos cellularum totaliter investienti- 

 bus sed unilateraliter anguste fissis; pyrenoideis conspicuis; cellulis 

 generativis non moniliformibus. 



Filaments short, somewhat contorted, lubricous, dark green, 16- 

 82;^, mostly 28-32/x diam.; cells short, 4^8/* long; cell wall 4-5;U. thick, 

 liomogeneous and hyaline; chromatophore broken slightly on one side, 

 but filling the length of the cell ; pyrenoid conspicuous, reproductive 

 cells not moniliform. 



Growing on rocks and on various other small algae, along high- 

 tide level or even above. Lands End, San Francisco, California. 

 Type no. 4125, Gardner, November, 1917. 



This is the only locality in which this species of Ulothrix has been 

 observed. It is quite inconspicuous, often being located on the shaded 

 portions of rocks, or obscured by the presence of other small algae, 

 Bangia, EnteromorpJia, Ulva, etc. It may grow in small tufts or, 

 more often, evenly, but rather sparsely, distributed. They are rarely 

 one centimeter long and are mostly only three to five millimeters long. 



This form seems scarcely to be distinguished from U. pseudoflacca 

 f. major (cf. "Wille, 1901, p. 22, pi. 2, figs. 64^81). It agrees almost 

 perfectly with AVille's description and figures, excepting in the size. 

 The filaments are from 16-36/^ in diameter, and the majority are of 

 the larger diameters, 28-32;u,. The diameters given for U. pseudoflacca 

 f. minor are 8-16ju, and for f. major are 10-22ju,. 



The gametangia are formed in. any of the cells without increase in 

 their diameter, however the length may be greater than in the vegeta- 

 tive cells. This is particularly noticeable in cells that have been 

 belated in forming gametes. The gametangia may become almost 

 spherical. 



Ulothrix pseudoflacca f. maxima is closely related to U. flacca 

 (Dillw.) Thur. That species is said to have a much greater range of 

 variation in the diameter of the filaments, and is a much longer plant. 

 The diameter as given by Collins (1909, p. 185) is 10-25/x, and finally 

 in the reproductive stage becomes 50jii in diameter. Farlow (1881, 

 p. 45) says that the filaments of U. flacca become monoliform. 



