70 Bulletin 186. 



On the Cotton, Gossy^num lierhacerirri. 



The Hhizoctonia which is the cause of "sore-shin " or damping 

 off of cotton seedlino^s has not yet been secured bv us ; but Professor 

 Atkinson lias kindly put at our disposal drawings which he made 

 while studying this fungus in Alabama. He first reported upon it 

 under the caption "sore-shin" in Bulletin 41 of the Ala. Agl. Exp. 

 Sta. In describing it, he says : " The diseased portion of the plant 

 is just beneath the surface of the ground, and is characterized by a 

 shrunken area of a dull reddish-brown color. ^^ -^^ * Jf the 

 injury remains coniined to the superficial tissues, the plant may, and 

 frequently does, recover." The sterile fungus concerned with this 

 disease was isolated, and inoculation experiments demonstrated that 

 the fungus secured was the cause of the dam ping-off. The descrip- 

 tion of the fungus in tlie above mentioned bulletin and the drawings 

 which we have, demonstrate beyond a doubt that the fungus is a 

 form of RMzoctonia. 



On the Lettuce, Lactuca sativa. 



Since 1896 we have repeatedly found lettuce seedlings damping 

 off by a sterile fungus; but it was not until 1898 that it was partic- 

 ularly studied, or its atiinities ascertained, and the fungus located 

 as RJiizoctonia. Lettuce seedlino-s affected bv this funo;ns have 

 much the same appearance as seedlings affected by any damping-off 

 fungus. At or near the surface of the ground the tissues become 

 water-soaked in appearance, tliey are unable longer to support the 

 plantlet, and it falls prostrate on the surface of the ground, the 

 funo'us soon invadino; all parts. This funo^us, under favorable con- 

 ditions may wilt down and destroy, within a day or two, whole 

 boxes of lettuce seedlings. The disease is also readily induced by 

 using pure cultures of the fungus for inoculation purposes. 



What is apparently tlie same fungus has been found several times 

 as a disease of maturer lettuce ])lants. After the presentation of a 

 preliminary report upon rhizoctonial diseases before the Society for 

 Plant Morphology and Physiology in New York, December, 1898, 

 we received from Mr. II. E. Smith, Andierst, Mass., lettuce plants 

 showing a severe rotting of the leaves. There was no doubt about 

 the characters of the fungus, and we determined it for Mr. Smith as 



