iv.] NEW DISEASE OF POTATOES. 19 



never attain a larger size than a grain of gunpowder, 

 others -are as large as peas or small beans. The " Native 

 Bread" or Mylitta of Australia, which often measures 

 several inches across, may be a Sclerotium. The edible 

 Americo-Indian Tuckahoo, which is dug out of the ground 

 in large masses, is not really a fungus, although so esteemed 



X'4-OO- 



FIG. 5. 



Section through outer surface of Sclerotium of Pesiza Postuma, B. and W. 

 Enlarged 400 diameters. 



by Fries, and named by him Pachyma cocos. Some Sclerotia 

 are sphaerical in shape, whilst others are elongated irregular 

 ovals. Sclerotia are not confined to one order or genus of 

 fungi, but they possibly occur throughout the entire family. 

 Some forms are much less compact than others, and the 

 looser forms germinate after a comparatively short rest. 



By means of Sclerotia certain fungi which would prob- 

 ably perish during drought or severe frost are preserved 

 alive through inclement seasons. The spawn naturally 

 compacts itself into these little hard masses and falls to 

 the ground ; it there remains, like a seed, uninjured by 

 continued cold or dryness, whereas the vitality of uncom- 



