Part 7

Key 4. Zygomycota

1 Spores formed in multispored sporangia (figs 68, 70, 72, 75, 76) or in few-spored sporangioles (figs 70, 73). 2 - Multispored sporangia and globose sporangioles absent. Spores formed singly on terminal, lateral or intermediate vesicles (figs 74, 79, 80, 82-86), or in short chains (figs 77, 78, 81). 11

2(1) Sporangiophore stout, simple, with a subsporangial swelling and a basal swelling buried in the substrate. Sporangia tough walled, black, projected some distance towards the light when mature, and sticking to whatever they hit. _Pilobolus_ (fig. 76) e.g. spores pale yellow, 8-10 × 5-6µm - _P. crystallinus_ spores orange, 12-20 × 6-10µm. - _P. kleinii_ - Sporangiophores not stout; sporangia not violently discharged. 3

3(2) Sporangial wall black, tough, not readily broken when touched. Sporangia with a sticky base, becoming attached to whatever they contact after the marked elongation of the white sporangiophores at maturity. _Pilaira_ (fig. 75) e.g. spores yellowish, 8-10 × 6µm - _P. anomala_ spores colourless, 11-13 × 6-8µm - _P. moreaui_ - Sporangial wall diffluent, spores readily removed in a droplet, or fragile and then spores easily dispersed by external violence. 4

4(3) Sporangiophores stiff and metallic in appearance, growing towards the light and often to great length (5-30cm). _Phycomyces_ e.g. spores 10.5-30 × 6.5-17µm; columella pyriform; sporangiophores up to 30cm - _P. nitens_ spores 8-13 × 5-7.5µm; columella spherical or ovoid; sporangiophores up to 30cm - _P. blakesleeanus_ - Sporangiophores white, not reaching extreme lengths. 5

5(4) Small lateral sporangia (sporangioles) present. 10 - Sporangioles absent. 6

6(5) Sporangiophores usually grouped, less often single, connected by stolon-like hyphae. 7 - Sporangiophores arising singly, or if grouped then lacking stolon-like hyphae. 9

7(6) Stolons joining groups of sporangiophores often with rhizoids at the base of the group. 8 - Sporangiophores arising singly or in groups from stolons, which may be 'rooted' at intervals along their length, but rarely beneath the groups of sporangiophores. _Absidia_ (fig. 71) e.g. sporangiophores grouped, rhizoids poorly developed; spores 2.5-4.5µm diam. - _A. corymbifera_ sporangiophores grouped, rhizoids strongly developed; spores 2.5-3.5µm diam. - _A. orchidis_

8(7) Sporangiophores mostly unbranched. _Rhizopus_ (fig. 69) e.g. spores irregularly angular-ovoid, 8-14 × 11µm - _R. nigricans_ - Sporangiophores with a whorl of branches beneath the main sporangium, each with a small columellate sporangium. Spores 6-8.5µm. _Actinomucor elegans_

9(6) Sporangia often with pigmented walls, yellowish when young, finally grey or black, with well marked columella left after spore dispersal. Individual sporangiophores observable with unaided eye, up to 20mm long. _Mucor_ (fig. 68) e.g. spores smooth, 7-8 × 2.5-4.5µm - _M. hiemalis_ spores smooth, 6-12 x 3-6µm - _M. mucedo_ spores asperulate, 5-8.µm diam. - _M. plumbeus_ (N.B. _Zygorhynchus_ would key out with _Mucor_. It is more often isolated from soil, and is distinguished from _Mucor_ by the presence of zygospores with unequal suspensors) - Sporangia white, without a columella, readily becoming a spore droplet. Sporangiophores delicate, often only 200-400µm long. Fine, white, garlic-smelling mycelium often present. _Mortierella_ (fig. 72) e.g. spores 16-27µm diam, few in each sporangium; sporangiophores ca 150µm, with short lateral branches at right angles - _M. reticulata_ spores 6-10 x 4-6µm; sporangiophores 2-3mm high, with ascending branches - _M. bainieri_ spores 4-10µm; sporangiophores richly branched - _M. candelabrum_

10(5) Sporangioles formed at the final tips of a densely dichotomous system of branchlets, originating some distance below a terminal sporangium (which may be absent in young specimens). Sporangioles up to 25µm diam., with up to 6 spores. Spores 8-12 × 6-8µm. _Thamnidium elegans_ (fig. 70) - Sporangioles either at the curved tips of slender branches, or clustered in groups about halfway along tapering branches which radiate from the sporangiophore below the sporangium; the branch tips of the latter give the fertile portion of the sporangiophore a bristly appearance. _Helicostylum_ (fig. 73) e.g. spores 8-17 × 3-7µm; sporangioles on short secondary or tertiary branches; fertile region bristly with sterile branches - _H. fresenii_ spores 6-8 × 4µm; sporangioles reflexed, on slender primary or secondary branches; fertile region without sterile branches - _H. pyriforme_

11(1) Spores formed in chains. 12 - Spores formed singly. 14

12(11) Sporangiophores regularly and repeatedly dichotomously branched. Chains of 2-10 spores produced in small groups, which may be wet or dry, on deciduous heads, 4-15µm diam. Parasitic on other fungi, mostly other Mucorales. _Piptocephalis_ (fig. 78) e.g. spores 4-5 × 2-3µm, in pairs; heads dry - _P. lepidula_ spores 5-6 × 2-2.5µm, in chains of 4-9; heads dry - _P. cylindrospora_ spores 4-8 × 2-4µm, in chains of 3-5; heads dry; sporangiophore without rhizoids - _P. freseniana_ spores 4-6 × 4-4.5µm, in chains of 3-6; heads wet; sporangiophore with rhizoids - _P. repens_ spores 3-5 × 2-2.5µm, in chains of 3-5, heads wet; head cell lyses, to leave only a fringe at the tip of the very fine sporangiophore - _P. fimbriata_ - Sporangiophores simple or irregularly branched. 13

13(12) A large conspicuous fungus, macroscopically Mucor-like, mycelium coarse. Sporangiophores with a distinct terminal swelling with crowded spore chains. Spores usually 5-10 in a chain, globose to ovoid, 2-8 × 4-6µm. _Syncephalastrum racemosum_ (fig. 81) - Sporangiophores less conspicuous, 100-1000µm high, with a 'holdfast' at the base attaching the sporangiophore to the substrate. Mycelium very fine. Parasitic on other Mucorales. _Syncephalis_ (fig. 77) e.g. sporangiophores 100-200µm high, with three 'nodes' along their length; merosporangia often forked at the basal cell; spores 8-10 × 6µm - _S. nodosa_ sporangiophores up to 750µm high; merosporangia usually subdivided at their base into several branches, each with 5-10 spores; spores 5-10 × 3-4µm - _S. depressa_ (N.B. _Oedocephalum_ spp. (fig. 79), the anamorphic states of many dung fungi (esp. Ascobolaceae and Pezizaceae), _Rhopalomyces_ (fig. 80), and some _Aspergillus_ spp. are superficially similar to _Syncephalis_ at first sight).

14(11) Sporangia containing a single closely fitting elongated spore, produced in serried ranks on one side of a boat-shaped branch (sporoclade). 15 - Single-spored sporangia ('spores') globose, produced singly or if in groups not on sporoclades. 16

15(14) Sporoclades lateral. Sporangiophores usually yellowish. (No parasitism has been demonstrated, but in culture grows much better in the presence of the white, garlic-smelling _Mortierella_ spp.). _Coemansia_ (fig. 82) e.g. spores 6-11µm long; sporoclades spirally arranged around the axis - _C. erecta_ spores 16-18µm long; sporoclades formed on one side of the axis, causing it to curve to one side - _C. scorpoidea_ - Sporoclades produced in a terminal verticil. Sporangiophores shining white. _Kickxella alabastrina_ (fig. 83)

16(14) Spores produced in clusters below the apex of the final branches of a compound, often trifid, branching system which is given a bristly appearance by the projecting tips. Superficially similar to _Thamnidium_ or _Helicostylum_. Capable of parasitising, and growing much better in association with, other Mucorales. _Chaetocladium_ (fig. 74) e.g. spores smooth, 4-6µm diam. - _C. brefeldii_ spores echinulate, 6.5-9.5µm - _C. jonesii_ - 'Spores' not produced in subterminal clusters, but terminally on lateral vesicles, or over the surface of swollen fertile regions of the sporangiophore. 17

17(16) Sporangiophores up to 250µm high. Lateral vesicles numerous, each producing a single 'spore', which is projected when mature. Parasitic on tardigiades. _Ballocephala_ (fig. 86) - Sporangiophores visible with the unaided eye. Spores produced on swollen parts of the sporangiophore. 18

18(17) Sporangiophores branched, with more or less globose terminal fertile regions. Spores dry and powdery, yellowish or pinkish in mass. _Cunninghamella_ (fig. 84) e.g. spores smooth, ovoid, 18-22 × 10-14µm or globose, 8-10µm diam. - _C. elegans_ spores echinulate, ovoid, 8-12µm - _C. africana_ - Sporangiophores unbranched, fertile portion 200-300 × 15-20µm. Fertile region terminal only, cylindrical. Spores smooth, greyish in mass, 2-4µm diam. _Mycotypha microspora_ (fig. 85) (N.B. _Ostracoderma epigea_ (fig. 85), the anamorph of _Peziza astracoderma_, which occurs on paper and sometimes dung and highly organic substrates, was originally described as _Mycotypha dichotoma_. The fertile regions are cylindrical but multiple as the result of several close dichotomous divisions at the base of the fertile portion).

Notes

[1] There are few reports of _Ascozonus_, apart from _A. woolhopensis_. Observed spore sizes of _A. woolhopensis_ suggest that measurement of Renny's (1874) illustrations of spores leads to values which are too large (19-20 × 6-6.5µm). Those in parentheses are what they might be, based on the discrepancy between observed values for _A. woolhopensis_ and Renny's illustration.