1920] Setchell-Gurdncr : Chlorophycme 293 



The presence of this endophyte in the fronds of species of Iridaea, 

 Gigartina and possibly also of Nitophyllum is indicated externally by 

 spots of a much redder color than that of the uninfested portions of 

 the host. Its detection at other points than about San Francisco will 

 probably follow careful search for it on similar hosts. 



28. Pseudodictyon Gardner 



Thallus much branched, the main filaments comparatively long and 

 tortuous, creeping among the cells of the cortical layer of the host 

 plant {Lamiinaria sp.), branching freely; the branches, usually aris- 

 ing at right angles to the main filaments and bending backward among 

 the cortical cells, unite into a sort of net ; a very short erect branch 

 composed of two or three cells arises from practically every cell of 

 the horizontal filaments in the central portion of the thallus; the 

 uppermost cell of each erect branch becomes a sporangium and grows 

 to the surface of the host; each cell contains a single peripheral 

 chromatophore with one pyrenoid ; reproduction unknown. 



Gardner, New Chlorophyceae, 1909, p. 374; West, Algae I, 1916, 



p. 304. 



Since neither the cytology nor the reproduction of the type and 

 only species thus far referred to this genus, has been studied, it exists 

 merely as a form genus of probably close relationship to Entocladia. 

 It is to be hoped that some one having favorable opportunity may add 

 much that is desirable to our knowledge of this seemingly very distinct 

 endophytic genus. 



Pseudodictyon geniculatum Gardner 

 Plate 11, figs. 5, 6 



The young, creeping filaments 3-4ju, diam., becoming larger with 

 age ; tips of the geniculate filaments seem to coalesce with neighboring 

 cells, giving the young plant the appearance of a fine net, the meshes 

 enclosing 4-8 cells of the host plant; sporangia 8-12jit diam.; cell 

 walls thin and cross walls distinct. 



Growing in abundance in the terminal parts of the blade of 

 Laminaria Sinclairii. San Francisco Bay, California. 



Gardner, New Chlorophyceae, 1909, p. 374, pi. 14, f. 5, 6 ; Collins, 

 Green Alg. N. A., 1909, p. 283 ; Collins, Holden and Setchell, Phyc. 

 Bor.-Amer. (Exsicc), no. 1628. 



