0LPIDI0P8ID M 1 \ I 



."> 1 



O. APPENDICULATA ilc Wildeman, 1898. I.C., p. 3*. 

 1896. \nn. Soc Beige Micro. W: 19. PL I. flgs. I. 8-19. 

 Pt0udolpidioptii apptndieulata (de Wildeman) Mto- 

 den, I..-., p. W9. 



Zoosporangia solitary, hyaline, smooth, spherical, 

 oval or ellipsoid with a single <xit tube which does 

 not project far beyond the surface of the host cell. 

 Zoospores unknown. Resting -.ports spherical. IS— 

 25 ,ii. thick-walled, covered with elongate abruptly 

 tapering, rather well separated spines; companion 

 cell single, hyaline, smooth, vermiform ami filamen- 

 tous, 20 /< long, anil inflated at the end; germination 



unknown. 



Parasitic in Mesocarpus sp., in Belgium, causing 



marked loeal swellings up to four times the normal 

 diameter of the filaments. 



O. OEDOGONIORUM Scherffel, 192S. Arch. Protisk. 



53: 109. PL I. figs. 199-207C! pi. 5, flgs, 207d-208. 

 O. furiformis var. Oedogoniarvm Sorokin, 1883. Arch. 



Bot Nord. Prance »: 39, fig. 31. 188!». Rev. Mycol. 



11: 89. PL 80, fig. !i9. 

 Olpidium Oedogoniarvm (?) de Wildeman, 1S9 1 . Ann. 



Soc. Beige Micro. 1*: 154. PL 6, figs. 9, 10. 



Zoosporangia solitary or numerous, up to 5 in a 

 cell, hyaline, smooth, oval, elongate, sac-like, 5—7 X 

 oO/i. with one or two short. 3-4 /j X 4-6 p., taper- 

 ing exit tubes which may project slightly beyond the 

 host cell. Zoospores isocont and diplanctic. hyaline, 

 oval and elongate, 5 p. long, with a small refringent 

 spot hut no conspicuous ventral furrow; flagella 

 lateral, one extending forward and the other hack- 

 ward in swimming; cystospores 3 p. in diameter. 

 Resting -.pores hyaline, smooth, spherical, oval, 

 ellipsoid. 10-12 p X M^. thick-walled; content 

 coarsely granular with several small refractive glob- 

 ules surrounding a large central one; resting spore 

 lying free within a hyaline, thin-walled, oval or 

 ellipsoid vesicle (oogonium ?) ; companion or male 

 cell solitary, hyaline, ova] or spherical, 10 p. germi- 

 nation unknown. 



Parasitic in Oedogonium sp.. in Hungary (Scher- 

 ffel. I.e.) and New York. U. S. A. (Sparrow. '33), 

 destroying the content of the algal cell but not caus- 

 ing hypertrophy. 



Scherffel believed that 0. futiformu var. Oedogo- 

 niarian Sorokin and Olpidium Oedogoniarum de 

 Wildeman are identical to this species. Fischer 

 ('92), however, listed Sorokin's fungus as a syn- 

 onym of Olpidium entophytum, while Minden re- 

 garded it as identical to de Wildeman's 0. Oedogo- 

 niarum. Since Sorokin and de Wildeman observed 

 only zoosporangia the questions of identity and 

 Synonomy of their species cannot be answered at 

 present, although both species occur in the same 

 host. 



The development of the resting spore in a vesicle, 

 which Scherffel and Sparrow interpreted as a true 

 oospore ill an oogonium without periplasm, and the 

 manner of zoospore formation and behavior are 

 strikingly similar to those of Lagenidium Oedogonu 

 Scherffel. while the thallus and zoosporangia are 



like those of Olpidioptu. For these reasons Scherffel 



WB.S uncertain as to which of the two genera this gpe 

 eies belongs and believed that it possibly may be B 

 transition form between Olpidiopsis and /. agt -m 

 (I in in. 



O. ANDREEI (Lagerheim) nov. comb. 



I'll uinirhi Ins iimlrii'i Lagerheim, 1899. Ymer 1: 136. 



/'. Ectocarpi Jokl, l!H(i. fjsterr. Bot. Zeitschr. ii(i: 267. 

 Pis. 1, ... 



Petersenia (Olpidiopsis) andrisi (Lagerheim) Spar- 

 row, 1936. Biol. Bull. 70: B45. Figs. 1-8, l-'. 



Zoosporangia solitary or numerous, up to 23 in a 

 Cell, spherical, 3— 80 fl, oval, ellipsoid, 8-15/xX 

 15—25 p., polygonal or irregular with 1-10 tapering 

 or irregular exit tubes, 3.5— 10 p. in diameter and 

 6—78 p long, which may penetrate adjacent cells and 

 project to the outside beyond the surface of the host, 

 or open within the host cell. Zoospores ellipsoid, 

 somewhat pyrif'orm, arched or curved 3 X 4—5 p, 

 with a large refractive spot at the narrow anterior 

 and broad posterior end ; occasionally liberated with- 

 in the host cell. Resting spores, parthenogenetic 

 (?) or sexual, spherical or slightly ellipsoid, 12— 

 23 p, brown, smooth and thick-walled; companion 

 or male cell when present single, hyaline, spherical, 

 5-12 p, or slightly oval; germinating by becoming 

 transformed directly into a zoosporangimn with an 

 exit tube. 



Weakly parasitic and possibly saprophytic in the 

 vegetative cells and plurilocular sporangia of Spon- 

 gomorpha sp.. in King Charles Land (Lagerheim, 

 I.e.); Acrosiphonia incurva, and Acrosipkonia sp.. 

 in Greenland and Denmark (Petersen. '05; Spar- 

 row, '34) ; Ectocarpus granulosus in the Gulf of 

 Trieste (Jokl, 'l(i), and E. siliculosus in Mass.. 

 U. S. A. (Sparrow, '36) ; causing slight hypertrophy 

 of the plurilocular sporangia in Ectocarpus, and de- 

 generation of the plastids and remainder of the pro- 

 toplasm. 



Although Sparrow placed this species in Peter- 

 senia, he nevertheless believed that it should be re- 

 ferred to Olpidiopsis. Its zoospores, however, are 

 strikingly like those of Pontisma. The male and fe- 

 male thalli which fuse to form the resting spore may 

 be equal in size or quite unequal, so that sexual re- 

 production in this species may be iso- or heterogam- 

 mis. according to Sparrow. Occasional resting spores 

 without attached empty male cells may also be 

 found, and they have doubtless developed parthc 

 nogenetically without fusion. 



Sparrow further regarded /'. Ectocarpi .lokl as 

 identical to this species, and the present writer is 

 listing it provisionally as a synonym. However, in- 

 asmuch as Jokl failed to observe flagellate zoospores 

 and resting spores its identity to 0. anilreei is very 

 doubtful at present. According to his observations. 

 the sporangia may occasionally occur extramatri- 

 cally and send their exit tubes into the algal cell (fig. 

 164). He further described and figured the newly- 

 entered zoospores and young thalli as naked and 

 ai boid with several long tenuous, more or less 



