YEASTS AND MOULDS. SSS 



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 fimgus 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 receptacles^ 

 containing conidia. When ripe the receptacles with their conidia 

 are detached at their bases, and spring 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 beU-glass. 



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

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

 famihar 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 carbonic 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 cells can, when the carbonic acid is withdrawn, germinate into 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 myceUum. They occur on bread and decaying vegetable 

 mat-ter. 



Mucor stolonifer (Lichtheim). — Mycehum 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. 



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

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



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

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



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

 spores. 



Mucor fusiger (Lichtheim). — Ovoid spores. 



