1985 - Mycological Society of America

ovine dung and on agar under controlled laboratory
conditions. The phaneroplasmodium is milky white.
This taxon typically forms white, subglobose sporangia
0.2 to 0.4 mrn in diameter. occasionally producing
straight or branched plasmodiocarps up to 1.5 mm in
length. It belongs to the group of Didymia with
crystalline, white, eggshell-like peridia. Some of
the larger fructifications contain crystalline bodies
attached to capillitial threads. A columella is
absent, and the fruiting bodies contain abundant,
typical didymiaceous capillitium. The spores are
echinulate, 9-10 pm in diameter, and subglobose,
encircled by an equatorial ridge that serves as the
site for spore wall dehiscence at germination. The
spores are reminiscent to those of Didymium saturnus
Keller. The sporangia of this new taxon resemble
Didymium nullifilum (Kow.) Farr, but differ in the
abundant capillitium and spores with an equatorial
ridge.
R. W. Kerrigan. Department of Biological
Sciences, University of California, Santa
Barbara, CA 93106. Systematics and
potential utilization of the genus Agaricus.
Phenotypic plasticity, apparent polymorphism,
and a lack of distinctive microfea tures complicate
the systematics of Agaricus at the
species level. It is less difficult, however,
to recognize infrageneric species
groupings. Biochemical features have become
increasingly important in delimiting sections
of Agaricus. The occurrence and properties
of mushroom phenoloxidases are particularly
useful in this regard. One section, Horten-
ses, comprises the widely cultivated species
- A. bisporus and its allies. The relationships
in this group appear to be quite close;
analysis on the basis of morphology alone is
difficult. Complementary biochemical and/or
molecular approaches would seem well suited
to the resolution of such problems.
The phylogeny of A. bisporus, and the
relationship of wild to cultivated strains,
is at present unclear. There are indications
that wild strains may have greater disease
resistance than do cultivated strains. There
may exist in nature a large and untapped pool
of genetic variation useful in crop improvement.
Study of the tetrasporic ancestral
complex may indicate how traits such as spore
number are controlled, perhaps leading to
cultivated heterothallic strains. Species
with different initiation requirements could
help to reveal how initiation proceeds.
R. W. Kerrigan and I. K. Ross. Department of
Biological Sciences, University of California,
Santa Barbara, CA 93106. Further
investigations of spore number in Agaricus.
Recent experiments and observations lend
further support to the concept of basidiospore
number as a dynamic phenomenon.
Earlier hypotheses regarding the influence of
sporocarp age and harves t-related stress on
spore number may have been incorrect. Low
temperature, on the other hand, has repeatedly
been found to cause a pronounced reduction
in average spore number. There are indications
of additional factors possibly influencing
the extent to which three- and twospored
basidia may occur in the hymenium of
predominately tetrasporic species.
Current knowledge regarding the nuclear
and/or genetic composition of spores borne
upon three- and two-spored basidia w i l l be
presented.
J.L.Kerwin,Christopher A.Simmons and R.K.Washino.
Dept. of Entomology, University of California, Davis,
CA 95616. Regulation of oosporogenesis by Lagenidium
giganteum.
Induction and maturation of Lagenidium giganteum oospores
are complex developmental processes influenced
by exogenous lipid media supplements and a variety of
calcium-dependent events. Sterols, which are necessary
for induction of oosporogenesis, enhance uptake of
fatty acids from growth media. Unsaturated 16- and
18-carbon fatty acids increase oospore induction and
maturation. Enrichment of the fatty acyl compounds of
the fungus with unsaturated moieties appears to affect
cyclic nucleotide metabolism and promotes cellular and
vesicular fusion events by regulating membrane fluidity.
Using a variety of inhibitory compounds, the
calcium-binding protein calmodulin and calcium-specific
channels have been implicated in L. giganteum oosporogenesis.
Hypotheses concerning the role of calcium
in regulating cellular and vesicular fusion are
presented.
ST. W. KIMBROUGH. Department of Botany, university
of Florida, Gainesville, FL 32611. The twilight
years of W. A. Murrill in Florida.
After resigning as Director-in-Chief of the New
York Botanical Garden in August, 1924, W. A. Murrill,
after a few years of wandering, settled in Florida
where he spent approximately 30 years around the
University of Florida in Gainesville. As noted by
Prof. George F. We3er (Mycologia 53: 543-557), Dr.
Murrill left the Garden as a very troubled man.
Health problems continued to plague him and were
perhaps responsible for his remaining in Gainesville.
Through the concern and attention of Professors
George Weber and Erdman West, Curator of the Herbarium,
Dr. Murrill was able to regain his strength
and composure. In was during his first summer months
in Gainesville that Dr. Murrill became enthused by
the large number of mushrooms that weremew to him.
His previous trips to Florida had evidently been
for short visits during the winter months.
During my first years in Gainesville, Prof. WeLer
and I were fortunate to have opportunities to visit
with Dr. Fred Seaver in Winter Park, Florida. It
was during these visits that I learned many interesting
things about Murrill and his activities. It is
these and other undocumented events that I would
like to present to you today.
Kimbrough, J. W., see Benny, G. L., et. al.
Kimbrough, J. W., see Gibson, J. L.
Kinney, A. J., see Rlackwell, Y., et. al.
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M. A. KLICH. U. S. D. A. Southern Regional
Research Center, P.O. Box 19687, New Orleans,
LA 70179. Prediction of the susceptibility of
cotton plants to invasion by Aspergillus
f lavus.
Cotton grown in the low desert areas of the USA
is susceptible to invasion by Aspergillus flavus
-.