94 FUNGOID PESTS OF CULTIVATED PLANTS. 



Potato Sclekote. 

 Sclerotinia Sclerotiorwn (Mass.), PI. VII. fig. 119. 



Curious hard fungoid bodies, having the nature and functions of a 

 resting mycelium, are sometimes found within the tissues of various 

 plants. These are called " Sclerotia," one form of which is known as 

 " Ergot." They vary much in size and appearance, but are commonly 

 oval or oblong with a dark outer coat, and an interior of compact cells. 



Potato haulms, all the parts above ground, have been known to 

 produce sclerotia in such numbers as to become a veritable pest. The 

 whole plant becomes covered with a thick felt of white mycelium, within 

 and without. The growth is very rapid, and ultimately numbers of small 

 sclerotia are produced amid the felt, from the size of a pin's head to that 

 of a bean. It was in 1883 that the ultimate development and destiny of 

 these sclerotia were discovered. 



When the sclerotia are placed in a favourable situation after a period 

 of rest, they commence to germinate. In this case it was a small fungus 

 called a Peziza which was produced. There was a cuplike or saucer- 

 like head, from a quarter to half an inch in diameter, proceeding from a 

 long slender flexuous stem, about two inches long, arising out of the 

 sclerotium. The inside of the cup is the fertile portion, and here long 

 cylindrical cells are closely packed side by side, each one enclosing eight 

 spores or sporidia, which are ejected when mature. The cup or Peziza was 

 called at first Peziza postuma, but has since acquired the name of 

 Sclerotinia. 



Fungicides are not likely to be of service, unless the disease is taken 

 in a very early stage, but the precaution should be taken of burning up the 

 diseased haulms to prevent the development of Peziza and spread of the 

 germs. 



Gard. Chron. Sept. 15, 1883; Mass. PI. Dis. 150, fig. 32; Tubcuf, 

 1 1 . 268 ; Smith, Field Crops, 25, fig. 3 &c. 



Potato Rhizoctonia. 



A serious Potato disease is announced in North America, caused by 

 Ehizoctonia Solani (Euhn). It was first observed in Long Island in 

 1900, and afterwards in Colorado, and is increasing in extent, so that 

 growers in Europe must be upon their guard. 



It is reported that large sines gave promise of an abundant yield, 

 but when digging time comes it is found that so few tubers have set 

 that it does not pay to dig them. Many vines do not produce a single 

 tuber. Il is by no means an uncommon occurrence for the vines to set 

 an abnormal number of small Potatos, or "little Potatos " as they are 

 f-all« d. These often occur in compact clusters, and are so small as to be 

 worthless. Another condition is the dying of Potato plants, all of 

 which conditions may be produced by attacks of Rhizoctonia. 



The hyphse of the fungus are often found on the surface and in the 

 scab ulcers of Potato , These hyphse give rise to irregularly shaped 

 dark masses known as sclerotia, which vary in size from that of a mere 

 speck. to half an inch or more in diameter. These sclerotia resemble 



