0LPIDI0P81DACKAG 



47 



to be true, all Achlya-inhaibit'mg parasites may pos 

 sibly be grouped as a single species with several pos 

 sible physiological races of varieties. To determine 

 this possibility an intensive study of the degree of 

 morphological variation of all species and their liost 

 range must be made. 



PARASITE OF APHANOMYCES 



O. APHANOMYCIS Cornu, I.e., p. 148, pi. 1, figs. 6-11. 

 Pti udolpidium Aphanomycit Fischer, I.e., p. 37. 

 <>. luxuriant Barrett, l.c.,p. 831. PI. 33, figs. 1, 5, 6, 9-14, 



In 18, .'II. .':i: pi. 84, figs. M :ii. 88 31; pi. -V.. figs. 

 t:i til: pi. 86. 



Zoosporangia Military or numerous, up to 20 or 

 more in a hypha, smooth, or spiny, spherical, oval, 

 fusiform and elongate, dimensions unknown; one to 

 several exit tubes which may extend considerably 



beyond the surface of the host cell. Zoospores iso- 

 cont, oval, egg- and slightly bean-shaped, size un- 

 known: coming to rest in a mass at the mouth of the 

 exit tube for a few minutes and then swimming away; 

 flagella inserted at (?) or near the anterior end. 

 Resting spores parthenogenetic or sexual, hrown, 

 oval, spherical, 25— SO p; endospore thick, exospore 

 comparatively thin and covered with conical spines, 

 2.5 p in height, or hlunt warts; contents granular 

 with one or more large refractive globules; com- 

 panion or male cells when present 1 to 3 per resting 

 spore, hyaline, smooth, oval, ellipsoid, spherical, 

 10-2.5 //, germination unknown. 



Parasitic in Aphanomyces sp. and Pythium sp. 

 - ) in France (Cornu, I.e.; Dangeard, '90); Apha- 

 nomyces sp.. in Denmark ( Petersen. '03, 09, '10) 

 and Germany (Minden, II); A. laevis in India 

 (Butler. '07; Sydow and Hutler, '07; Butler and 

 Bishy, '3 1 ) and the U. S. A. (Barrett. I.e.; Shanor, 

 '39. 10) and A. cladogamous (Whiffen, 12) caus- 

 ing large broadly fusiform intercalary and almost 

 spherical terminal swellings in the host hyphae. 



As noted above, Dangeard reported this species 

 as a parasite of Pythium, but Butler ('07) and 

 Shanor were unable to secure infection of P. mono- 

 spermunt, P. proliferum, P. gracile, and /'. aphani- 



dermatum with it. Butler nevertheless believed that 

 tin- resting spore figured by Dangeard relates to 0. 

 dphanomycet, but as Minden (11) and Shanor 

 :;!i suggested it is probably the resting spore of 

 0. [Pseudolpidium) Pythii. Shanor (10) was un- 

 able to transfer O. A phanomycis to Aphanomyces 

 itellatut, Achlya, Saprolegnia and other water 

 molds, and concluded that it is limited in host range 

 to Aphanomyces laevis. Miss Whiffen, however, re- 

 ported its occurrence in ./. cladogamOUS. It is to be 

 noted, however, that her fungus did not infect ./. 

 laevis, which suggests at once that it may be a 

 physiological race of <). Aphanomycis. This remains 

 to be shown, however, from more extensive cross 

 inoculation experiments involving Saprolegnia, 

 Achhia and other similar host species. 



PARASITES OK l'YTIIUM 



O. PYTHII (lintler) comb. nov. 



Pteudolpidium Pythii Butler. 1907. Mini. Dept. Agrlc. 



India. Hot. Ser. 1 No. 5:127. PI. 7, figs. !> Hi. 



Zoosporangia solitary or numerous, hyaline, 

 smooth, oval, and ellipsoid, up to 35 p. in the great 

 est diameter, with a single exit tube of varying 

 length which extends for a short distance beyond the 

 surface of the host. Zoospores isOCOnt, hyaline, uni 

 equilateral, somewhat kidney-shaped with one lo 

 several small refractive granules; flagella laterally 

 inserted; swarming in the vicinity of the exit canal 

 for a brief period, then coming to rest for a few 

 minutes in a dense cluster; finally swimming away 

 slowly. Resting spores parthenogenetic. solitary or 

 numerous, often in association with zoosporangia. 

 oval or spherical, 19.2— 30 /x, brown, comparatively 

 thin-walled and covered with fine, thread-like, short, 

 evenly spaced spines; germination unknown; com- 

 panion or male cells lacking. 



Parasitic in Pythium monospermum, P. rostra- 

 turn, P. vexans, and P. intermedium in France (But- 

 ler, I.e.), Pythium sp.. in Germany (Minden. '11), 

 P. oryzae in Japan (Tokunaga, '33), and Pythium 

 sp., in England (Sparrow, '36), causing oval, spher- 

 ical, obpyriform or balloon-shaped enlargements at 

 the end of the host hyphae or in lateral diverticula, 

 and occasionally leading to septation of the hyphae. 



O. GRACILE (Hutler) comb. nov. 



P. gracile Hutler, I.e., p. 129, pi. 7, figs. 1-8. 



Zoosporangia solitary or numerous, up to 10 in a 

 single swelling, hyaline, smooth or spiny, spherical, 

 •1—52 /x, with 1 to 5 contorted and swollen exit tubes 

 of varying lengths which may project considerably 

 beyond the surface of the host cell. Zoospores, iso- 

 eont ( ?). hyaline, obclavate. elongate, and some- 

 what curved with one to several minute refractive 

 granules, size unknown; one flagellum inserted near 

 the anterior end, the other laterally; swimming mo- 

 tion smooth, body of spore often revolving on its 

 long axis. Resting spores parthenogenetic, single 

 or numerous, occurring in association with the zoo- 

 sporangia. spherical to oval. 12— 27 p exclusive of 

 spines, yellowish, containing a large refractive glob- 

 ule surrounded by a peripheral layer of vacuolate 

 protoplasm; endospore .7 to 1.2 p. thick, exospore 

 1.7 to 2.5 p thick and covered with long. 1 p., taper- 

 ing, thick, crowded spines; germination unknown; 

 companion or male cells lacking. 



Parasitic in Pythium intermedium in France 



( Butler. I.e.) and P. rostratum in the I". S. A. 

 (Whiffen, 12) causing terminal enlargements and 

 Lateral, oval- or balloon-shaped diverticula in tin- 

 host hyphae which may be 80— 90 p in their greatest 



diameter. 



Whether the zoospores are hi -terocont or isocont 

 is not certain from Butler's description. He reported 

 that one Hagellum is inserted near the anterior end 

 while the second I is lateral, but his figure (fig. 



