oll'llilol'sin ICE \K 



H 



may cause ■ localised temporary agitation of tin- 

 host protoplasm, according to McLarty. The refrac- 

 tive granules in the latter swirl in eddies around the 

 young parasite (fig. 10) and soon obscure it from 

 view. This reaction, however, is of short duration, 

 because when the parasite again becomes visible it 

 is closely surrounded by the host protoplasm and 

 hardly distinguishable from ordinary protoplasmic 

 inclusions. The two protoplasts appear to be inti- 

 mately associated, and no visible antagonism is ex- 

 hibited. At hast, there is no retraetion of the host 

 protoplasm away from the parasite. The host nuclei 



appear normal in its immediate vicinity and appar- 

 ently are not stimulated to divide by its presence. In 



0. ickenkiana (fig. 133), 0. Oedogoniorum, and 0. 

 andreei (fig. 162 |, as noted before, tin- young para- 

 site migrates toward and becomes closely applied to 

 the host nucleus, and in the ease of 0. andreei (P. 

 Ectocarpii) may completely engulf it. 



As the thalli increase in size the free floating phase 

 ends and the parasites Income more or less localized 

 in the hyphae. At this stage the host protoplasm be- 

 gins to How toward and accumulates around the 

 thalli. and in a short time hypertrophy of the host 

 begins. In some instances the swelling appears to be 

 initiated in the immediate vicinity of the parasite, 

 hut this is not the general rule. Furthermore, hyper- 

 trophy does not invariably occur. In some oogonia 

 and hyphae containing limited amounts of proto- 

 plasm McLarty found little or no distortion follow- 

 ing infection by 0. Achlyae. Accordingly, he be- 

 lieved that the swellings are not due to direct stimu- 

 lation by the parasite but to the great accumulation 

 of the host protoplasm in its immediate vicinity. 

 That the host wall is stretched in such regions has 

 been demonstrated by Diebl's ('35) plasmolytic ex- 

 periments. 



As the swellings increase in size conspicuous 

 vacuoles appear in the host protoplasm (figs. 1. 54). 

 These soon become traversed by more or less radiat- 

 ing strands of protoplasm moving slowly towards 

 the parasite. This movement continues until all or 

 most of the protoplasm has been attracted to and ab- 

 sorbed by the developing thalli. In the species which 

 parasitize green algae the plastids and nuclei art- 

 destroyed, and at maturity the sporangia (tig. 1-16) 

 and resting spores are partly surrounded by a mass 

 of degenerated protoplasm. In 0. Ricciae on Riccia, 

 however, no harmful effects are apparent, accord 

 bug to du Plessis. This species occurs only in the 

 rhizoids and basal swelling of the same, and al- 

 though they become infected when young they de- 

 velop normally. No distortion, swelling, rupture or 

 necrotic effects are produced, and du Ph-ssis accord- 

 ingly believed that the relationship between host and 

 fungus may possibly be symbiotic. 



PARASITES OF SAPROLEGNIA 



O. SAPROLEGNIAE ( Braun) Cornu, I.e.. ),. I 15. PI. :i, 

 figs. 1-10. 



Chytridium Saprolegniae Braun, 1855a, Ber. K'gl. 

 i'n-iiss Akad, \\iss. is.-,;,: 384. 1855b. Abh. K'gl. Akad, 



«iss. Berlin is:,;,: (il. PI. .",, ftg. -':!. 



oipitliiiiu Baprolegniat Braun, I.e.. p. ".">. 

 Diplophysa Saprolegniae Schroeter, 1886. Cohn's Krj 



pt'fl. Schlesiens :i: L95. 

 I'.-i mini /liiliii hi Saprolegniae Fischer (pro parte) 1892. 



Rabenhorst's Krypt'fl. I, t: 85. 

 OlpidiopsU echinata Petersen, 1909. Hoi. Tidsskr. 39: 



405. Pig. XVIIIa. 1910. Ann. Mycol. 8: 540. Fig. 



X Villa. 



Zoosporangia usually numerous in a host cell, 

 hyaline, smooth or spiny (?), variable in size and 

 shape, spherical, 15-150 /i, oval. (i7 /i )< 00-100/*, 

 ellipsoid and elongate 15-25 p X 20-150 p, with 

 one to several short or elongate, straight, curved, or 

 irregular exit tubes which end Hush with the surface 

 of the host cell or extend considerably beyond it. 

 Zoospores isocont ( ? ). oval, or slightly bean-shaped 

 with the flagella attached near the anterior end. 

 Resting spores parthenogenetic (?) or sexual, 

 brown, oval spherical, 28-107/*; endospore thick, 

 exospore covered with numerous short (?) spines; 

 companion or male cells when present 1 to 4 per 

 resting spore, hyaline, smooth, oval, spherical, 18— 

 32 p; germination unknown. 



Parasitic in Saprolegnia sp., S. fcrajc, S. fhitreti, 

 and S. mixta in Germany [Nageli, '44 (?); Braun, 

 '55a, '55b; Pringsbeim, '60; Reinseh, '78 (?); 

 Behla, '03; Minden, '11; Diehl, '35]; Saprolegnia 

 sp., in France [Cornu. I.e.; Dangeard, '00; Varit- 

 chak, '31 (?)], Russia (Sorokin, '83, '80), Rou- 

 mania (Constantineanu, 01); S. dioica and S. 

 monoica in Denmark ( Petersen, '00, '10) ; S. thureti, 

 S. diclina, S. delica, S. mixta, S. littoralis, S. mono- 

 ica, Saprolegnia sp., Isoachlya anisospora, I. uni- 

 spura, and /. recent rica in the U. S. A. (Barrett, 

 '12; Davis, '14; Schwarze. '22; Harvey, '27. '42; 

 Graff. '28; Maneval. '37; Shanor, '40; Couch. '41; 

 Wolf. '41); S. thureti and >S. monilifera in Japan 

 (Tokunaga, '33) causing large terminal and inter- 

 calary swellings in the host hyphae. 



According to Shanor, this species is limited in 

 host range to species of Saprolegnia and Isoaclili/a 



and will not infect Achlya, Aphanomyces, Aplanes, 

 Dictyuchus, Leptolegnia and Protoachlya species. 

 If this is true, the parasites described by Petersen 

 ('09, '10). Coker ('23). Gilman and Archer ('20) 

 and Sparrow i '32. '33) as O. Saprolegniae in Ach- 

 lya relate to another species, unless these workers 

 were mistaken about the identity of the host plants. 

 Sparrow ('83) was of the opinion that Coker's fun- 

 gus is 0. luxurians, but this .seems unlikely since tin- 

 latter species is confined to . / plm mini geex hosts, ae 

 cording to Shanor ('40). Inasmuch as Coker inter- 

 preted 0. Saprolegniae in the sense of Fischer i '92 I, 

 it is not improbable that the species which he ob- 

 served in A. flagellata and ./. imperfecta may pos 

 sibly be (). fusiformU or 0. various. In view of tin- 

 fact that sporangium size and shape and the char- 

 acter of the exospore an- no longer diagnosl ie.ill v 

 specific, and in the light of Shanor's contentions 

 that the species are restricted to certain hosts, it is 



