282 TUFTS COLLEGE STUDIES, VOL. II, No. 3 



5. ACROCHAETE Pringsheim, 1862, p. i. 

 Epiphytic or endophytic ; filaments creeping, branching, artic- 

 ulate, bearing short erect branches, which often end in a slender 

 tube containing a long, slender seta ; chromatophore parietal, 

 with one or more pyrenoids ; sporangia formed from terminal 

 cells of erect branches, bearing no setae, producing many bicili- 

 ate zoospores, which germinate to produce the parent form ; 

 sexual reproduction reported, but uncertain. Marine. 



KEY TO THE SPECIES OF ACROCHAETE. 



i. Cells seldom 2 diam. long. 2. A. parasitica. 



i. Cells longer, 2-6 diam. i. A. repens. 



1. A. REPENS Pringsheim, 1862, p. 2, PL II; P. B.-A., 

 No. 1279. Creeping filaments 7-9 p. diam., cells 2-6 diam. long, 

 usually with several pyrenoids; sporangia elongate-ovoid, 8-12 

 X 20-40 /A. Fig. 101. In the cortical layer of Chorda filum, 

 Laminaria, etc. Mass. Europe. 



The setae are sometimes very abundant in this species, some- 

 times so rare that a careful examination is needed to find any. 



2. A. PARASITICA Oltmanns, 1894, p. 208, PI. VII, figs, i- 

 10 ; Rosenvinge, 1898, p. 114. Creeping filaments 8-12 it diam., 

 cells about i^ diam. long, with disk-shaped chromatophore and 

 one pyrenoid ; sporangia somewhat clavate, usually projecting 

 above the surface of the host plant, about 25X10-12 p.. In old 

 fronds of Fucus. Greenland. Europe. 



6. ENDOPHYTON Gardner, 1909, p. 371. 

 Filaments endophytic in red algae, sparingly and irregularly 



branched in the medulla of the host, more freely near the sur- 

 face ; cells with band-shaped chromatophore and one pyrenoid ; 

 sporangia at the surface of the host, on short erect branches, 

 producing pyriform, biciliate zoospores. 



E. RAMOSUM Gardner, 1909, p. 372, PI. XIV, figs. 3 and 4. 

 Filaments 4-6 it diam., often tortuous and irregular, cells 6-8 

 diam. long; sporangia clavate, 10-12 //. diam., pointed when 

 young ; zoospores numerous, 3 /x diam., escaping by an opening 

 at the end of the sporangium. Fig. 121. In fronds of Iridaea 

 laminaroides Bory, Gigartina radula (Esper)J. Ag. Cal. 



Forming patches usually a few mm. diam., but which may be 

 confluent and cover considerable areas, usually near the base 

 of the frond of the host. In Gigartina the patches show more 

 reddish than the rest of the frond. 



7. PSEUDODICTYON Gardner, 1909, p. 374. 



Filaments endophytic in larger algae, much branched, long 



