CHAPTEE X. 



MOULD OF ONIONS. 



Mucor subtilissimus, B. 



THE fungi known as Mucors or Moulds (muJces, mould) 

 are extremely common on decaying bulbs, fruits, pro- 

 visions, etc. They are said not to be the immediate cause 

 of decay, but there can be no doubt that they greatly 

 accelerate putrescence when they grow upon exposed or 

 injured places. Sometimes they grow in the inner sub- 

 stance of plants, like the one under description, which has 

 been named by the Kev. M. J. Berkeley, in reference to its 

 extreme smallness and delicacy, Mucor subtilissimus. 



A species of fungus closely allied to the onion Mucor is 

 the common Mucor mucedo, L., so frequent on paste, jam 4 

 damaged fruit, etc. The onion Mucor differs from all its 

 allies, t in its extremely small size ; it is said to be the 

 most microscopic of all fungi found in Great Britain. 



In the Mucor disease the whole substance of the neck 

 of the onion near the bulb, and sometimes the bulb itself, 

 is traversed by fine threads of mycelium, and in the midst 

 of this mass of spawn may be seen innumerable black 

 atoms like minute grains of gunpowder. These little 

 grains have been described as fungi under the name of 

 Sclerotium Gepce and Sclerotium cepcevorum, B. ; the nature 

 of Sclerotia is described under Peziza postuma, B. and 

 Wils. The present Sclerotia not only differ from the 

 potato Sclerotia in their much smaller, almost microscopic 

 size, but also in their less compact and more filamentous 

 structure. The less compact a Sclerotium is, the more 

 readily it will germinate, and in the present instance the 



