Saprolegnia - The iLumina Digital Library

irregular; unbranched, branched, or forming a glomerulus. Oospores centric or
subcentric; spherical or compressed at one side, or ellipsoidal; 1-2 (-4) per oogonium,
and generally not filling it; (l6-) 32-38 (-43) µm in diameter; germination not observed.
Antheridial apparatus absent.
Saprolegnia unispora is recognized chiefly by its short-stalked, large, generally
spherical oogonia (often in glomeruli or on once-branched stalks) usually containing a
single, large, centric or subcentric oospore, but having no attendant antheridial
filaments. Thus, in all essential features but one -- the lack of an antheridial apparatus --
S. unispora is hardly distinguishable from S. megasperma (compare Figs. 93 H, 100 K).
Nolan (1975a), in fact, theorized that S. unispora might represent part of an evolutionary
trend from S. megasperma through a form of the latter possessing what were alleged to
be parasitic antheridial branches.
Although Saprolegnia unispora shares with S. itoana the characteristic of a single
oospore (predominantly) in each oogonium (Fig. 100 C-H), these species are unlike in
two other features of taxonomic value. The oogonial stalks of S. itoana (formerly
recognized as S. subterranea by Seymour, 1970) are consistently longer than those of S.
unispora. Moreover, S. itoana usually forms antheridia whereas S. unispora is not known
to do so.
Coker and Couch (Coker, loc. cit., pl. 23, fig. 12) describe the oospores of Isoachlya
(=Saprolegnia) unispora as centric, but the illustration of the “...ripe...” eggs depicts them
unmistakably as subcentric. This error is repeated in Coker and Matthews (1937). In all
probability the S. unisperma referred to by Dick (1973:138) was S. unispora.
CONFIRMED RECORDS: -- AUSTRALIA: Cookson (1937:241). BRITISH ISLES:
R. A. Couch (1951:107, p1s. 19-21). CANADA: Maestres (1977:149, fig. 64).
CZECHOSLOVAKIA: Cejp (1959a:199, fig. 70g-l). INDIA: Dayal (1958:50, pl. 2). JAPAN:
Okane (1977:6, figs. W, X). REPUBLIC OF CHINA: Volz et al. (1974:231, fig. 8). UNITED
STATES: R. L. Butler (1975: figs. 49-52); Coker and Couch (loc. cit.); Seymour (loc. cit.); A.
W. Ziegler (1948b:19, pl. 2, figs. 7-11; pl. 3, fig. 1; 1952: 8, pl. 2, fig. 10). USSR:
Morochkovs’kii et al. (1967: 134, fig. 120).
RECORDED COLLECTIONS: -- BRITISH ISLES: Apinis (1964); Cook and
Morgan (1934). CANADA: Dick (1971c); Maestres and Nolan (1978). GERMANY:
Höhnk (1935a; 1956a). INDIA: Dayal (1959). JAPAN: Okane (1978); Suzuki (1961f, i).
NEW ZEALAND: Karling (1966f). REPUBLIC OF CHINA: Liu and Volz (1977). SOUTH
AMERICA: Upadhyay (1967). UNITED STATES: G. C. Hughes (1959, 1962); T. W.
Johnson (1956a); T. W. Johnson and Surratt (1955); V. D. Matthews (1935); Scott (1960b);
Slifkin (1964); A. W. Ziegler (1958b). USSR: Dudka (1965, 1966); Logvinenko and
Meshcheryakova (1971).
SPECIMENS EXAMINED: -- UNITED STATES (11), TWJ, RLS. Centraalbureau
(2).
Saprolegnia megasperma Coker
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