PLATE VIIL— COMMON BROWN MOULD (Mucor nmcedo). 



(Conjugation after Bre/vhi.) 



This Mould is to be found in damp, close places growing on a variety of substances. It may be obtained in a form suitable for 

 examination either from bones, or from potatoes which have been pared and boiled. If the latter are allowed to stand for a few days 

 in a covered dish, they produce a luxuriant crop. Mucor affords a good illustration of a simple form of the sexual process, in which 

 two perfectly similar and stationary elements unite or conjugate, and produce a body capable of reproducing the plant. 



Nuclei have been observed, although not shown in the drawings. 



Fig. 1. Full-grown Mycelium developed from the gonidium. 



The gonidium sends out various prolongations, which branch in all directions, so that the entire mycelium is 

 formed, consisting of a tubular single cell. But at a further stage septa are formed in various parts, so that it 

 becomes multi-cellular. 



From a swelling an % aerial branch arises, terminating in the young sporangium. 

 Fig. 2. Sporangium containing spores. 



The swollen head of the aerial hypha becomes divided off by a partition, and this bulging up into the interior 

 constitutes the Columella. 



The Sporangium-wall becomes coated with needle-like crystals of oxalate of lime. 



The Endo-gonidia are formed from the protoplasm in the interior and become coated with a cellulose wall. 

 The residue of the protoplasm forms an intermediate substance capable of swelling. 

 Fig. 3. Ruptured Sporangium. 



The sporangium having imbibed moisture swells. The outermost layer is brittle but not distensible, so with 

 the swelling of the innermost layer and the intermediate substance, it bursts, setting free the gonidia, and often 

 leaving a remnant in the torn collar. 



Figs. 4 and 5. Gonidia germinating. 



The outer coat of the spore is inelastic, and the inner protrudes as a filament, growing and branching till it 

 becomes full-grown, as in Fig. i. 



Fig. 6. Gonidia are not only produced by aerial hyphae, but not unfrequently from old submerged hyphae. Septa arise close to 

 one another, forming distinct joints, and these become rounded off, fall away, and are able, under favourable conditions, 

 to germinate. These bodies are the so-called Mucor-yeast or Chlamy do-spores (Lat. chlamys, a cloak). 



Fig. 7. The sexual process — Conjugation. 



Branches from two adjacent filaments of the Mycelium, approach, the double wall between them is absorbed, 

 and on each side of the central portion a partition is formed, thus marking off the Zygospore. 



Fig. 8. Ripe Zygospore with thickened granulated outer wall. 



Fig. 9. Zygospore germinating. 



It produces a single hypha, which sends up an aerial branch forming a Sporangium in which Endo-gonidia are 

 produced in the ordinary way. 



Life History of Mucor. — The mycelium of Mucor produces upright branches in the swollen ends of which gonidia are produced, 

 giving rise, on germination, to a new Mucor, or submerged hyphae produce gonidia with the same result. This mode of 

 multiplication is non-sexual, but sexual reproduction also occurs. Two short branches unite end to end, forming a Zygos- 

 pore. This Zygospore germinates, producing an upright branch with a sporangium at the end, and the gonidia give rise to 

 the non-sexual generation as at first. 



