152 PLANT DISEASES 



on the ground until the following spring, when they give 

 origin to usually several more or less funnel-shaped, brown 

 ascophores supported on long, slender, crooked, dark- 

 coloured stems. 



The spores are ejected from the asci at maturity, and 

 germinate at once, soon forming a vigorous mycelium 

 amongst dead organic matter, which afterwards becomes 

 parasitic, attacking the stems of annual plants near the 

 ground-line, and acting as already described. It was 

 shown by De Bary that the earliest mycelium formed after 

 germination cannot penetrate living tissues as a parasite, 

 but must first live for some time as a saprophyte. 



In addition to attacking the stems of living plants, this 

 fungus often proves very destructive to tubers and roots 

 stored for the winter, as dahlias, artichokes, beetroot, and 

 more especially carrots, surrounding the tubers with a 

 white cottony mycelium which rapidly causes rotting and 

 decay, the mycelium of the fungus becoming studded with 

 black sclerotia, varying from i line to half an inch or more 

 in length. The rapidity of the disease is much intensified 

 if there is any tendency to ' sweating ' in the stored roots. 



De Bary states that this species does not possess a 

 Botrytis stage ; other later observers, however, incline to 

 the idea that this condition is sometimes produced. 



PREVENTIVE MEANS. A difficult fungus to combat. 

 Disease stems containing sclerotia should be collected and 

 burned, as should also diseased tubers and roots. 



Where the disease has previously existed, and there is a 

 probability of the presence of sclerotia in the soil, it would 

 be well to sprinkle the surface with soot or quicklime, 

 which would destroy the mycelium during its period of 

 saprophytic existence, previous to attacking the young 



