LAGENIDIALES 971 



stage of Sirolpidium can be surely identified and compared with that of 

 Pontisma, there is still good reason to keep the two separate. 



Pontisma lagenidioides H. E. Petersen 

 Oversigt Kgl. Danske Vidensk. Selskabs. Forhandl., 1905(5): 482, rig. X, 1-3 



Sirolpidium lagenidioides (Petersen) Karling, Simple Holocarpic Biflagellate 

 Phycomycetes, p. 66. 1942. 



Thallus at maturity ordinarily composed of a linear series of some- 

 what irregularly cylindrical simple or short-branched segments 20-60 [i 

 or more long by 1 1-30 u. in diameter, slightly constricted or sometimes 

 almost disarticulated at the narrow cross walls, olpidioid thalli 14-16 [x 

 long by 13-15 \± high and tubular nonseptate thalli 130-200 u. long 

 occasionally produced; sporangia generally forming a single narrowly 

 cylindrical slightly tapering discharge tube (sometimes several) of 

 variable length (up to 145 \x), the tip of which, at least, is extramatrical ; 

 zoospores numerous, somewhat bent, rod-shaped, reniform, or pyri- 

 form, 2.5-3 u. in diameter by 4.5-7 [i in length, with a strongly refractive 

 region at either end and two short laterally attached oppositely directed 

 flagella, swarming within the sporangium before emerging by flagellar 

 action through the discharge tube, movement erratic, tumbling; resting 

 spore spherical, somewhat thick-walled, 27 u. in diameter, with several 

 refractive oil drops. 



Weakly parasitic or saprophytic in Ceramium rubrum, C. strictum, C. 

 fruticulosum, Petersen {loc. cit.), Sparrow (1934c: 11, pi. 3, figs. A-H), 

 Denmark; saprophytic in Ceramium diaphanum, Sparrow (1936b: 252, 

 pi. 1, fig. 5), United States; Ceramium sp., Hohnk (1939: 340, fig. 2, 

 a-g), Germany; Ceramium diaphanum, Aleem (1950c: 714, figs. 3-4; 

 1950d : 43 1, figs. 17 19), Ceramium tenuissimum, J. Feldmann (1954: 

 1 34), J. and G. Feldmann (1955: 246, fig. 5), France : Ceramium rubrum, 

 C.pedicel/atum, C. corticatulum, Aleem (1953: 16, figs. 32-33), Sweden: 

 ? Cladophora japonica, Kobayashi and Ookubo (1953 : 63, fig. 8), Japan. 



Zoospores of this species closely resemble those figured by Butler 

 (1907) for "Pleolpidium inflation Butler," a parasite of Pythium. Accord- 

 ing to Hohnk (1939), they have only one refractive region— at the 

 forward end. 



