231 
Species of Olpi diop sis, (Cornu) Fischer . 
Cornu’s illustration (PI. Ill, Fig. io) of the oospore of this species 
certainly clearly shows definite spines on the mature oospore rather than 
warts or tubercles. 
A. Fischer ( 13 ), in 1892, described what he considered as O. Sapro- 
legniae as possessing resting spores with the outer wall thickly covered 
with hemispherical or blunt colourless warts up to 3 ju high. I am unable 
to reconcile this with Cornu’s description. I believe that Fischer was dealing 
with a distinct and new species for which, as previously stated, I propose the 
name O. vexans. 
Olpidiopsis vexans , nov. sp. 
Synon. O. Saprolegniae , A. Fischer, 1892. Rabenhorst’s ‘ Krypto- 
gamenflora von Deutschland ’, I, lv, 38. 
Sporangia, single or multiple, formed in terminal or intercalary swellings 
of the host hyphae, elliptical, oval, or spherical, very variable in size, up to 
176 ju, in diam., with smooth, colourless membrane, colourless contents, 
and one to several unbranched exit tubes ; zoospores elongated, slightly 
inequilateral, with two cilia attached at or near the anterior end. Oospores 
dark grey, with one, sometimes two, antheridial cells ; oospores surrounded 
by a thick endospore and a thin warty exospore, spherical to oval, sometimes 
elliptical, up to 116 x 841a, average 50 jut in diam. ; antheridia spherical, less 
commonly oval, average diam. 20 /q with a smooth, colourless wall. Germi- 
nation of oospores not observed. 
Zoosporangiis solitariis v. numerosis, in cellula matricis terminalibus v. 
intercalaribus viventibus, ellipsoideis, ovalibus, v. sphaericis, magnitudine 
variis, 50-176 ju, diam., hyalinis, membrana tenui, levi ; zoosporis numerosis, 
elongatis ; ciliis duobus, apici v. proximis apici insertis ; oosporis, griseis, 
sphaericis ad ovalia, interdum ellipsoideis, circ. 116 x 84^ (saepissime 50 \l 
diam.), endosporio crasso, levi, episporio tenui, verrucoso ; cellulis antheri- 
diis hyalinis, sphaericis ad ovalia, membrana tenui, levi cinctis, 20 /x diam. 
Hab. in Saprolegnia per ax, Ithaca, N.Y. 
Olpidiopsis luxurious, nov. sp. 
Sporangia single or multiple, formed in terminal or intercalary swellings 
of the host hyphae, oval to spherical, very variable in size, with one to three 
exit tubes extending considerably beyond the wall of the host ; zoospores 
rather small, elongated, with two cilia 'attached at or near the anterior end. 
Oospores spherical, with one or two, rarely three, antheridia, with a thick 
endospore and a thin exospore provided with numerous conical spines up to 
2*5 p in length ; oospores 25-50 fj, in diam., contain one or more large oil 
globules ; antheridia spherical, frequently oval to elliptical, 10-25 diam., 
with a smooth colourless wall. Germination of oospores not observed. 
Parasitic in Aphanomyces laevis , de Bary, Ithaca. 
Zoosporangiis solitariis v. numerosis, in cellula matricis plerumque 
intercalaribus viventibus, ovalibus ad sphaerica, magnitudine variis, collo 1-3 
