authors have proposed a treatment asincertae
sedis (Hibbett et al. 2007 ). Although apo-
morphic exobasidiomycetous morphological
features like septal pore caps and local inter-
action zones are lacking, at least in Malasse-
ziales, we follow the proposal of Begerow et al.
( 2006 ) based on molecular data (Fig.11.7). All
orders are presented alphabetically without
additional hierarchy.
a) Ceraceosorales
Within Exobasidiomycetes, theCeraceosorales
are characterized by intracellular hyphae with
a simple interaction apparatus (Fig. 11.6)
(Begerow et al. 2006 ). Theseptal pores inCer-
aceosorus bombacis(B.K. Bakshi) B.K. Bakshi
are simple and enclosed by membrane caps at
both sides(Fig.11.5a), as seen in Melanotae-
niaceae of the Ustilaginomycetes and in Micro-
stromatales, Entylomatales, Doassansiales, and
Exobasidiales of the Exobasidiomycetes (Bauer
et al. 1997 ; Begerow et al. 2006 ). InCeraceosorus
and in Brachybasidiaceae, basidia protrude
through stomata or emerge from the disinte-
grated epidermis. The basidia are elongated,
basally thick-walled, and two-sterigmate and
form ballistosporic basidiospores with an adax-
ial orientation of the hilar appendices in both
groups (Begerow et al. 2002 ; Cunningham et al.
1976 ). Like Brachybasidiaceae and Exobasidio-
mycetes in general,Ceraceosorusproduces local
interaction zones (Begerow et al. 2006 ). How-
ever, molecular data do not support a closer
relationship between Exobasidiales and Cera-
ceosorales (Fig.11.7). The other Exobasidiomy-
cetes lacking an interaction apparatus or
establishing a simple interaction apparatus,
such as Entylomatales, Georgefischeriales,
Microstromatales, and Tilletiales, do not form
intracellular hyphae or haustoria (Bauer et al.
1997 ; Begerow et al. 2006 ). Thus,C. bombacis
(B.K. Bakshi) B.K. Bakshi seems to be isolated,
and the monotypic order seems to be justified.
b) Doassansiales
Acomplex interaction apparatus, including
cytoplasmic compartments, characterizes this
order (Figs.11.4cand11.6) (Bauer et al. 1997 ).
The studiedspecies of this group have parasitic
hyphae with clamps. They are teliosporic and
dimorphic and do not form ballistoconidia in
the haploid phase. The teliospore germinates
with holobasidia (Fig. 11.3g) (Bauer et al.
1999a;Va ́nky et al. 1998 ). The members of
Burrillia, Doassansia, Entylomaster, Hetero-
doassansia,Nannfeldtiomyces,Narasimhania,
Pseudodoassansia,Pseudodermatosporus,Pseu-
dotracya, andTracyahave complex spore balls
(Va ́nky 1987 , 2012 ), whereas Doassinga
(Fig. 11.1a), Melaniella, and Rhamphospora
produce single spores (Va ́nky 1994 ;Va ́nky
et al. 1998 ).The spore balls differ in the occur-
rence of sterile cells within the spore ball.In
addition, teliospores are darkly coloured in
Melaniellaand lightly coloured inDoassinga,
Rhamphospora, and genera with complex telio-
spore balls. The hosts of the Doassansiales are
systematically diverse, comprising spike
mosses (Selaginellaceae) and various monocots
as well as eudicots.
However, members of Doassansiales
are ecologically well characterized by their
occurrence on paludal or aquatic plants, or
at least on plants of moist habitats. They
apparently evolved in the ecological niche of
aquatic plants and developed complex spore
balls and more or less sigmoid basidiospores
in adaptation to water dispersal (Fig. 11.3g)
(Bauer et al. 1997 ). Interestingly, the species
of Doassansiopsis in Urocystidales likewise
parasitize aquatic plants and possess similar
complex spore balls. Thus, Doassansiopsis
and Doassansiales are excellent examples of
the independent, convergent evolution of simi-
lar structures under the same environmental
condition.The order comprises three families. Ultrastructural and
LSU sequence analyses revealed a basal dichotomy
between Melaniellaceae presenting pigmented spores
and Rhamphosporeaceae and Doassansiaceae showing
hyaline teliospores (Bauer et al.1999a; Begerow et al.
1997 ). In contrast to members of Doassansiaceae,
Rhamphospora nymphaeaeD. Cunn., the only species
placed in the Rhamphosporaceae, forms highly
branched haustoria (Fig.11.8) (Bauer et al. 1997 ).Ustilaginomycotina 313