F. J. F. SHAW. i 7 



IxOtULATlONS. 



In order to ;^ro\v the rice plants under sterile conditions the 

 method used by WHrd(l;J)in hi.- investigations on tluj rust of 

 wheat was employed. The seeds were tirst sterih-^^ed in 1% com- 

 mercial formaline and then sown in sterile potato tubes containing'" 

 Knop's solution. It was found that sterilisation wa- more 

 efficient if performed under the air punjp. the hquid, in tlii.'^ way, 

 penetrating the space between the glumes njore readily. Owinf' 

 to the laboratory temperature in February being rather low for 

 the growth of rice, the tubes were kept in an incubator at a tem- 

 perature of oO' C. The incubator was left with its gla>s door 

 facing a large north window, and. for several hour> in the njiddle 

 of the day, the tubes were removed and placed in the >un 



The young plants were iiifected when they were about 7 — 10 

 days old and about 3 — 4 inches high. The first series of infeciious 

 was made with small black sclerotia I'rom an agar culture about 

 one month old. None of these inoculations gave any result, the 

 sclerotia failing to germinate. Subsequent trials with sclerotia 

 fronj old cultures showed that they had, not infre'|uentlv. lost the 

 power of germination. Fresh inoculations were then made from 

 a culture three days old. in wliieli the hy[jhce were .-t^till growing 

 vigorously, and sclerotia were noi yet feanied. A small speck of 

 agar was removed from such a culture and placed ujjon a rice 

 culm, about 1 inch above the remnant of the seed : hyphnj quickly 

 spread from this ceiitre over the exterior of the cuhn, which 

 gradually lost its green colour and turned brown near the seat 

 of infection. As the outer leaf -heath turns brown, the lamina 

 attached to it also loses its green colour and wilts (PI. I, Figs. 

 2, 3) ; finally, the process extends to the centi^al leaves, and the 

 whole plant dies. During the progress of the infection a light 

 weft of hyphte can be seen investing the culm : in the later stages 

 of the disease small, dense, white aggregations of hyphai appear 

 in this mycelium, and, ultimately, become hard black sclerotia of 

 the usual type. This superficial production of sclerotia is a charac- 

 teristic of the section Libera of this genus. We have, however, 

 seen that sclerotia may arise in the more deep-seated portions 



