138 



MORPHOtOGY AND PARASITISM OF RHIZOCTONI A. 



From the above table it will be seen that jute seed is very sensi- 

 tive to naphthaline. Methods, such as this, which aim at destroy- 

 ing the fungus in the soil, must be distinguished from others, which 

 merely ensure the planting of clean seeds. In the case of tul)ers 

 (e.g., potato), and plants (cr/., ground nut) which ripen their seed below 

 the ground level, some means of disinfecting diseased seed should 

 l)e adopted. Rolfs (24) found that treatment of diseased ])otato 

 seed with corrosive sublimate or formalin considerably impioved 

 the outturn ; this method, however, must be combined with suitable 

 and systematic rotation in order to give the best results. 



Identity ok the kungus. 

 The commonest species of Rhlzoctonia appears to be R. riola- 

 ww Tul., under which name Saccardo includes R. Medica(/inis D. C. 

 and R. Solani Kiiliii. Kiihii gives a careful (Icsciiptioii of these 

 two forms and states that the piincipal dilTcicncc between them lies 

 in the sclerotium ; in both cases this is a smkiII loiiiid black structure, 

 l)Ut that of R. Holani is smooth while that of R. Mcdicoffitus is 

 covered with hyjiha*. A com|)ari.soii of Fig. 1. I'l. IX. in this paper 

 with Taf. \'1I, Fig. 21 oi Kiihii sliows the essential siiiiilaiit \- 

 between the sclerotium of //. <So/«/// and that of the fdim desciilied 

 above : moreover, the scicrotial fungus wliieh (kiuis lui [mtato 



