THE FUNGUS FAMILY. 



103 



sionally attacked by mildew, such as wheat, peas, and turnips, 

 whole fields of the latter becoming white in a single night. 



The great extent and sudden appearance of mildew gives 

 a reason for much speculation as to its origin and propaga- 

 tion, of which even a summary would occupy too much 

 space here. Many species of fungi having the nature of mil- 

 dew are common to fruits, as apples and pears, commencing 

 sometimes from a wound in the skin, the jointed filaments of 

 the fungus soon entirely enveloping the fruit. In other cases, 

 apples, &c., without any apparent external blemish, are 

 affected, the whole substance becoming perforated by the 

 fibres, which soon causes them to rot. Sometimes pears per- 

 fectly sound to all appearance, are unpalatable through the 

 presence of fungi, which renders them extremely bitter. The 

 spots found on linen after being folded up for a long time are 

 due to some kind of mildew. 



Smut-dust (Ustilago segeturri). A common form of mil- 

 dew found on grasses, but its effects on wheat are of a 

 formidable character, doing great injury. It affects the ear 

 in its earliest stage, completely destroying the young grain, 

 and causing the whole to become a swollen mass of black, 

 sooty dust. 



Bunt, or Pepper-brand ( Ustilago foetidd). Wheat is at- 

 tacked with this as by the preceding, but in this case the ear 

 is only partially affected, some of the grains being left perfect, 

 while that affected becomes filled with dust of a foetid odour, 

 distinguishing it from the smut or dust-brand which is scent- 

 less. In both cases the dust is the spores or organs by which 

 the plants are reproduced, and with these the ground, and 

 also the sound grains become impregnated. Experiments 

 made by the celebrated microscopist, Francis Bauer, show 

 that the spores are absorbed into the tissues of the plant, and 

 carried up till they reach the ear, where they develope and 

 multiply to the destruction of the grain. 



Ergot (Oidium ahortifaciens). A microscopic mildew com- 

 mon to grasses, attacking one or more of the young grains in 

 the ear, which it affects in such a manner as to cause it to 



