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A. DISEASE OF CAULIFLOWER AND CABBAGE CAUSED BY 



SCLEROTINIA. 



BY GEORGE GRANT HEDGCOCK. 



The cabbage, cauliflower, and related plants are more 

 often diseased by the black rot due to Pseudomonas cam- 

 pestris (Pammel) Smith than by all other causes combined. 

 During the past two years plants of both cauliflower and 

 cabbage have been observed at the Missouri Botanical 

 Garden and elsewhere in the vicinity, decaying with a dark 

 rot, often accompanied by numerous tiny black specks. 

 This at first was thought to be a form of the bacterial rot. 

 When specific cases on the cauliflower were brought to our 

 immediate attention, the differences between this disease 

 and the bacterial one were noted. Cultures carefully 

 taken from the interior of decaying cauliflower stems, 

 quite uniformly produced colonies of a fungus with a 

 white, fluffy mycelium. These were transferred and the 

 fungus studied throughout all its stages and identified as 

 Sclerotinia Libertiana Fckl. It has been grown under 

 careful bacteriological methods, and inoculations have been 



made, the results of which verify its nature as a parasite, 

 and also confirm the investigations of Ralph E. Smith on 

 Botrylis and Sclei'otinia.* 



The rot of cauliflower produced by Sclerotinia Liber- 

 liana is more watery than that caused by Pseudomonas 

 campestrisy and the diseased tissues are not so dark in 

 color. Sclerotia are not always present, and when found 

 are usually sparse in number. The fungus penetrates 

 through the cell walls of the host in every direction, caus- 

 ing a collapse of the cell walls, and wherever the epidermis 

 becomes ruptured a rapid escape of the protoplasm of the 



Bot. Gaz. 29:369-406. (Jun. 30, 1900). 



(149) 



