YEASTS AND MOULDS. 583 



wall, the filament reaches an intercellular space, where the mycelium 

 develops. This continues to grow and spread throughout the plant. 

 In tubers it can hibernate and develop in the young shoots in the 

 following spring. The fungus appears in the form of brown 

 patches on the green parts of the plants, especially the leaves. 

 The attacked parts wither and turn yellow or brown in colour. 

 If the under surface of a diseased leaf is examined, a corresponding 

 dark spot may be observed, accompanied with a faint greyish-white 

 bloom, which covers it. The latter consists of the conidia-bearing 

 branches. 



Pilobolus — ^The fruit-hyphse possess spherical receptacle.^ 

 containing conidia. When ripe the receptacles with their conidia 

 are detached at their bases, and spiing by their elasticity to some 

 distance. The fungus occurs as glassy tufts on the excrement of 

 cows, horses, etc. A cultivation can generally be obtained by 

 keeping fresh horse-dung under a bell-glass. 



Mucor mucedo. — Hyphse colourless, simple or branched ; spo- 

 rangia yellowish-brown or black ; spores ovoid. They form the 

 familiar white mould on fruits, bread, potatoes and excreta, and 

 penetrate into the interior of nuts and apples. A network of 

 fibrils develops in the substance of nutrient gelatine, with forma- 

 tion of sporangia on the free surface. The germination of the 

 spores and development into hyphse can be observed in a few 

 hours if the fungus be cultivated in a decoction of horse-dung. 



Mucor racemosus Hyphse short ; sporangia, yellowish to 



pale-brown ; spores round. By continued cultivation in liquids 

 saturated with cai'bonic acid, the hyphse become still shorter 

 and exhibit a yeast-like sprouting. These yeast-like or toruloid 

 cells can, when the carbonic acid is withdrawn, germinate into 

 normal mycelium. They occur on bread and decaying vegetable 

 matter. 



Mucor stolonifer (Lichtheim). — Mycelium grows in the air and 

 then bends down and re-enters the nutrient substratum ; sporangia 

 black, and spores globular. The mycelium can penetrate through 

 the shell of eggs, and, form conidiophores within them. 



Mucor aspergillus (Lichtheim). — Fruit-hyphse thinned at the 

 base, and with many fork-Uke divisions ; dark-brown spores. 



Mucor phycomyces (Lichtheim). — Mycelium thick-walled; 

 olive-green fruit-hyphse ; black sporangia, and oblong spores. 



Mucor raacrocarpus (Lichtheim). — Spindle-formed, pointed 

 spores. 



Mucor fusiger (Lichtheim). — Ovoid spores. 



