•14. 



THE SIMPLE 1IOLOCAHPIC BIELAGELLATE 1'HYCOMYCKTES 



tensive tests under varying environmental conditions 

 may produce different results. 



Diehl made an intensive biological study of this 

 species by growing its host under various cultural 

 environmental conditions. He found that the young 

 thalli may change their position in the galls regard- 

 less of the streaming of the host protoplasm and thus 

 show independent amoeboid movement to some de- 

 gree in the young stages of development. When in- 

 fected hyphae of the host are transferred to agar 

 the exit tubes of the parasite may grow out into fila- 

 ments 200 jx to 567 /a long. Under such cultural con- 

 ditions, the sporangia may mature and produce nor- 

 mal zoospores. Diehl has also found that resting 

 spore formation occurs abundantly at low tempera- 

 tures, and that 1 to 3 so-called male thalli may fuse 

 with the larger female cell. 



O. SAPROLEGNIAE var. laevis Coker, 1933. The Sapro- 

 legniaceae, p. 185. PI. 62, figs. 1-6. 



Zoosporangia solitary or up to seven in a cell, 

 hyaline, smooth, spherical, oval, ellipsoid with 1—2 

 tapering exit tubes of variable length which project 

 only slightly beyond the host cell. Zoospores small. 

 Resting spores oval or elliptical, thick-walled and 

 smooth; companion cells, 1-2, spherical, oval, ellip- 

 tical, hyaline, and smooth; germination unknown. 



Parasitic in Saprolegnia ferax and S. monoica in 

 North Carolina, U. S. A. 



O. INCRASSATA Cornu, I.e., p. 116, pi. 4, fig. 12. 



O. Saprolegniae Fischer, I.e., pp. 34, 38. 



O. major Maurizio, 1895. Jahresb. Nat. Ges. Grau- 

 bundens 38: 15, figs. 4-9. 



O. vexnns Barrett, 1912. Ann. But. 36: 231. 

 » Pseud ol pidiiun incrassatum (Cornu) Fischer, I.e., p. 37. 



Zoosporangia solitary or numerous, up to 12 or 

 more in a host hypha, hyaline, smooth, or covered 

 with spines of various lengths, thicknesses, and 

 abundance; spherical, 20-176 /x, oval ellipsoid, 

 6-30 /a X 90-121 it. or elongate with 1 to 7 straight 

 or curved, coiled, stout or filamentous and occasion- 

 ally branched exit tubes of varying lengths. Zoo- 

 spores isocont, oval, ellipsoid and somewhat elon- 

 gate, slightly flattened on one side ; flagella attached 

 near the anterior end. Resting spores parthenogene- 

 tic or sexual, spherical, 30—60 fi, oval, ellipsoid, 

 40-80 /a X 80-1 16 /a, rarely elongate, 5X105 /a; 

 exospore dark greyish-brown, thin and warty, or 

 thick, undulating and wavy in contour, hyaline (?), 

 yellowish-brown or bright-golden in color; endo- 

 spore fairly thin or thick ; contents coarsely granu- 

 lar with one to several small or large refractive glob- 

 ules ; companion or male cells when present 1 to 4 

 per resting spore, hyaline and smooth, spherical, 

 18-30 /j., oval, 15-20 X 20-32 /a; germination un- 

 known. 



Parasitic in Achlya racemosa (?) in France 

 (Cornu, I.e.) and Denmark (Petersen, '09, 10); 

 Achlya sp. ( ?) in Russia (Sorokin, '83, '89) and the 

 U. S. A. (Sparrow, '33); Saprolef/nia thureti, and 

 S. monoica in Germany (Fischer, '92) ; S. thureti 



and S. hypogyna in Switzerland (Maurizio, I.e.); 

 S. ferax, S. diclina, S. delica, S. mixta, S. monoica 

 (?), S. littoralis, Isoachlya anisospora and /. uni- 

 spora in the U. S. A. (Barrett, I.e.; Shanor, '39, 

 '10), causing large terminal clavate swellings in the 

 host hyphae. 



According to Cornu this species is characterized 

 by resting spores with a yellowish-brown wavy or 

 undulating exospore as is shown in figure 98. The 

 inclusion, however, of other species with wartv and 

 knobby resting spore as synonyms of O. incrassata 

 changes this original distinction, and it is now im- 

 possible to distinguish this species by the character 

 of the exospore alone. 



Maurizio's O. major (fig. 99) is apparently the 

 same as O. incrassata, but whether or not Fischer's 

 O. Saprolegniae and Barrett's O. vexans are identi- 

 cal to Cornu's species may be open to question. 

 Shanor ('40) came to the conclusion that they are 

 identical as a result of his cross inoculation experi- 

 ments. As is shown in table 1, he found that O. in- 

 crassata is limited in host range to species of Sapro- 

 legnia and Isoachlya and will not infect Achlya. For 

 this reason the present writer has inserted question 

 marks after the Achlya species listed in the above 

 host index. However, the number of Shanor's mono- 

 zoospore infections is quite small, but if the general 

 conclusion to be drawn from his results are con- 

 firmed it is obvious that the reports of Cornu, Soro- 

 kin, Petersen and Sparrow that O. incrassata oc- 

 curs in Achlya species are incorrect. Shanor held 

 that Cornu was probably in error about the identity 

 of his host plants, since no apparent attempt was 

 made to obtain them in pure culture for accurate 

 identification. Shanor further pointed out that in- 

 fected hosts often became so distorted and atrophied 

 that identification is impossible unless they are 

 grown in pure culture. Whether or not Sorokin, 

 Petersen, and Sparrow also were mistaken about 

 their host plants is impossible to determine at pres- 

 ent. On the other hand, the possible existence of 

 biological races of 0. incrassata which parasitize 

 Achlya must not be ignored in discussions of the host 

 range of this and other Olpidiopsis species. Sorokin 

 saw only oblong zoosporangia and no resting spores, 

 so that it is not certain that lie was dealing with O. 

 incrassata. Fischer ('92) believed that Sorokin's 

 fungus relates to O. fusiformis (P. fusiforme) in- 

 stead of to the former species. Sparrow observed 

 nothing but ellipsoid resting spores with a hyaline 

 undulating wall, which differs in color from the 

 golden yellowish-brown exospore described by 

 Cornu and Maurizio. As noted elsewhere, Petersen 

 believed that O. incrassata (P. incrassatum) Cornu 

 is identical to O. Saprolegniae (P. Saprolegniae) 

 Fischer and listed it as a synonym of the latter spe- 

 cies. 



O. IRREGULARIS Constantineanu, 1901. Rev. Gen. Bot. 

 13: 373, figs. 76, 77. 



Zoosporangia solitary or up to 15 in a hypha, hya- 

 line, smooth, oval, elongate, lobed and very irregu- 



