can be relatively small and hemispherical (often
compressed) inBackusellaand several other
thamnidiaceous Mucorales, discoid, or even
lacking in the unispored sporangiola of species
ofBenjaminiella,Chaetocladium,Dichotomocla-
dium,andMycotypha (Benny and Benjamin
1975 , 1976 ; Benny et al. 1985 ).
c) Merosporangia
Merosporangia are simple or branched
endospore-forming structures that contain 1–
20 or more spores. The multispored forms are
usually more or less cylindrical, whereas uni-
spored merosporangia can be variously shaped.
In multispored taxa the spores are usually
borne uniseriately, except inSyncephalastrum
racemosum Schroeter, where the occasional
spore may be biseriate. The merosporangial
wall can be evanescent or persistent. Merospor-
angia are formed in one family (Syncephalas-
traceae) of Mucorales [Fig. 8.4(40)] and in
Dimargaritales, Kickxellales [Fig.8.2(19, 22)]
(Benjamin 1959 ), and some members of Zoo-
pagales [Fig.8.5(44, 47)] (Piptocephalidaceae).
- Thallospores
a) Arthrospores
Arthrospores are formed singly or in chains
from vegetative hyphae with a primary func-
tion of dissemination.The cells swell as they
mature, and a relatively thin, secondary wall is
deposited inside the primary wall. The arthros-
pores ofEllisomyces(Mucorales) are dehisced
either rhexolytically or schizolytically (Beakes
et al. 1984 ). The asexual propagules ofHelico-
cephalum(Zoopagales) are arthrospores (Bar-
ron 1975 ).
b) Chlamydospores
Chlamydospores are formed in swellings that
arise in coenocytic, young hyphae. These
spores are borne singly or in chains, interca-
lary or terminal, often thick-walled cells with
perennation as the primary function[Fig.8.4
(38)] (Griffiths 1974 ). The ontogeny of chlamy-
dospores has been observed, using light and
transmission electron microscopy, inGilber-
Fig. 8.5Representatives of only order (Zoopagales) of
Zoopagomycotina. 42. Sporophore and fertile vesicle
bearing some pigmented, unispored sporangiola of
Rhopalomyces strangulatus. 43. Portion of fertile head
ofThamnocephalis sphaerosporashowing septate fertile
hyphae, and fertile vesicles bearing unispored sporan-
giola. 44. A few terminal branches of Piptocephalis
xenophilabearing numerous multispored merosporan-
gia. 45. Young zygospore of Piptocephalis lepidula
showing suspensors that lack vesicles.46–48.Syncepha-
lis hypogena. 46. Typical sporophore and zygospore. 47.
Asexual reproductive structure (rhizoids, sporophore,
globose vesicle, merosporangia) showing merosporan-
gia borne on bottom of vesicle. 48. Typical zygospore
(top right) borne on vesiculate suspensors. 42 .Bar
100 mm.43–48.Bar 50 mm228 G.L. Benny et al.