APPENDIX. 227 



thickness. Twigs with as many as five branches, each 

 bearing an egg-shaped conidium. The contents of the 

 conidia falling off* and reaching a drop of moisture, break 

 up into a number of swarming zoogonidia, which in 

 turn develop upon plants. Fixing themselves to the 

 cuticle of the host, they throw a germinating filament into 

 an epidermal cell ; piercing first its outer wall, and then 

 its inner wall, the filament reaches an intercellular space, 

 where the mycelium develops. This continues to grow 

 and spread throughout the plant. In tubers it can hiber- 

 nate and develop in the young shoots in the following 

 spring. The parasites appear 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 

 be 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 of the fungus. 



Pilobolus. Hyphae, I 2 mm, high. Fruit-hyphae, 

 possessing 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 mould 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. Hyphae, colourless, simple or 

 branched, I 15 cm. long, sporangia are yellowish-brown 

 or black. Spores ovoid, *oo8 mm. long, and "0037 wide. 

 Occurring as the familiar white mould on fruits, bread, 

 potatoes, excreta, and penetrating into the interior of 

 nuts and apples. A network of fibrils develops in the 

 substance of nutrient gelatine, with formation of sporangia 

 on the free surface. The germination of the spores and 

 development into hyphae can be observed in a few hours, 

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



Mucor racemosus. Hyphae, at most i -5 cm. long 



