WIG] 



1'AKASITIC KHIZOCTONIAS IN 



323 



CORN, Zea mays 



In 1914, during the progress of the soil survey for R. Solani the 

 fungus was found frequently on corn roots in the field. It could not 

 be determined whether the fungus penetrated the roots or not but 

 there was no question as to the abundance of the mycelium on the 

 roots. 



Rolfs 95 in 1905 reported Corticium Vagum B. & C. on corn in 

 Florida. 



COTTON, Gossypium lierbacsum 



Glover 40 in 1855 described a 

 respects is the same as the disease 



FIG. 13.-STEMS OF YOUNG CARNA- 

 TION PLANTS INOCULATED WITH 

 KmzocTONiA FROM COTTON, 

 SHOWING LESIONS CHARACTERIS- 

 TIC OF SORE SHIN OF COTTON 

 CAUSED BY THE SAME FUNGUS 



sore shin of cotton, which in some 

 of seedling cotton caused by Rhizoc- 

 tonia. He stated that ' ' the cause is 

 attributed by many to cold, cutting 

 winds, when the plant is very 

 young. Others, however, assert that 

 when a high wind shakes a tender 

 plant, the main stem is so much 

 bent and twisted that the sap ves- 

 sels are upturned and a serious in- 

 jury occurs." 



One of the causes of sore-shin 

 disease of cotton remained undis- 

 covered until Atkinson, 5 in 1896, 

 found in the diseased tissues a ster- 

 ile mycelium, which he later identi- 

 fied as Rhizoctonia. By means of 

 pure-culture methods and inocula- 

 tion experiments he further proved 



that this sterile fun ^ us was th e 

 cause of sore shin and also of seed- 



n n g ro t and damping-off of cotton. 

 TT j -u AT. T-T.- 



He Ascribes the Rhizoctonia dis- 



ease of cotton as follows : 



' ' There are several phases of the disease. Sometimes the tissues undergo a 

 soft rot which progresses very rapidly, and the early stages are not marked by any 

 striking color characteristics. Another phase may progress rapidly or slowly and 

 is usually quite well characterized by a reddish brown color which accompanies it. 

 This phase is also characteristic in that it is usually manifested on one side of " 

 the stem in the form of an ulcer which gradually deepens until the vascular sys- 

 tem is reached, when the life of the plant becomes really endangered. Even when 

 this stage is reached, however, the plant may, and does frequently, recover. 



"This latter phase is characteristic of a very common disease of seedling 

 cotton. It is called by the planters in many places 'sore shin.' 



* ' The diseased portion of the plant is just beneath the surface of the ground 

 and presents an area of shrunken tissue of a dull brown or reddish color. The 



