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Helminthosporium sp.: Superficially resemble
Drechslera, bipolaris and exserohilum spores but
the mechanism of sporulation is quite different.
The taxonomy of this entire group has been widely
debated. The antigen labeled Helminthosporium
in use by allergists for skin testing has been
neither Drechslera or bipolaris. No cases of infection
caused by true Helminthosporium have been reported
in humans or animals. No information is available
regarding toxicity. Allergenicity has not been
studied, although cross reactivity may exist between
all the above-mentioned genera. Natural habitat
includes dead stems of herbaceous plants, and
twigs and branches of many different kinds of
tress. Helminthosporium solani is the cause of
silver scarf disease in potatoes.
Histoplasma sp.: A fungus that has filamentous
growth at 25 degrees C and yeast growth at 37
degrees C. It is reported to be a human pathogen.
It may be associated with birds.
Humicuola: Grow on products with a high cellulose
content. These fungi are also found in soil and
on plant debris.
Hyaline Mycelia: Sterile mycelia that is white
or transparent. No fruiting structures are produced
by the mycelia. Visual identification of these
organism is not possible. Often associated with
Hyalodendron sp.: Appear to be common during
certain periods of the year. They are morphologically
related to Cladosporium but do not have the olive
and brown pigments of Cladosporium. No information
regarding health effects, toxicity, or allergenicity
is available. May be identified on surfaces by
tape lifts, tease mounts from bulk samples and
in air by culturable samples. Spores look very
close to Cladosporium and would most probably
be thought of as young undigested
Cladosporium spores on spore trap samples. Natural
habitat is most probably woody plant materials.
Hyphal-like fragments: Filamentous. Branched
structures with cell walls.
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