158 RED ROT OF SUCiAKCANE. 



inoculated trench, while tluMc wore 340 in the coiitiol trench and 784 

 in the trench further away. 



A form of CoUetotrlchuni falmtuHi which is truly parasitic 

 on the leaves of sugarcane, was described and hgured on page 13 and 

 plate III, fig. 9 of the previous Memoir, and has also been found in 

 Louisiana.' The ability of this form to cause typical red rot when 

 introduced through setts has been demonstrated, as the following 

 experiments show. As these experiments have a definite bearing 

 on the question of the propagation of the disease through the setts 

 they are included here, though the leaf form of the fungus will be 

 more fully considered below. 



On December 5th, 1907, 21 canes of Red Mauritius were 

 inoculated from a pure culture of the leaf parasite shak'cn up in 

 distilled water. The inoculations were done by reinoving a cyhnder 

 of cane at a lower internode witli a small sterile cork borer, inserting 

 some of the culture in the wound and replacing the cylinder after 

 cutting a piece off the end with a flamed knife, so as to leave a cavity. 

 The stem was then l)()und with fine steiile gutta-percha sheeting. ( )n 

 March 6th, 1908, the inoculated canes were cut and examined. One 

 had been damaged by a jackal and was discarded. The others were 

 outwardly sound. With 18 of these a trench was planted on March 

 7th, the canes being cut into the usual setts each with three " eyes." 

 In cutting it was observed that obvious reddening of the pith occurred 

 in from 1 to 3 internodes al)ove the seat of inoculation. The remain- 

 ing two canes were examined microscopically and the presence of Col- 

 letotrichum demonstrated. A similar trench was planted alongside, 

 with sound setts from the same plot, to serve as a control. The condi- 

 tion on May 30th is shown graphically below. Red rot was severe 

 in the inoculated trench and practically absent in the other. 



Im/caLaled canr 



e oo oo 



Control 



I Edgertou, C. \V., loc. cil., p. 4, PI. I. 



