IG A SCLEROTIAL DISEASE OF RICE. 



liyphic at tirst spread over the surfaee uf the agar, and slowly turn 

 a brownish eolour where they are in eoiitaet with the nutrient 

 medium ; the aerial hyphtu, however, remain white. Sclerotia 

 arise first upon the surfaee of the agar, but, ultimately, may be 

 found imbedded in it at various depths. At a level of about 

 \ inch below the surface of the agar the hypha) form a dense 

 brownish black layer, which, upon examination, is seen to consist 

 of an enormous number of chlamydospores. These chlaniydos- 

 pures are formed by the segmentation of the hypha3 into a 

 number of short thick barrel-shaped cells. They possess thick 

 Ijlack cell walls and contain food reserve in the form of oil drops 

 (PI. II, Fig. 9). Germination gives rise to a culture of the 

 u<jrmal type. 



Growth upc^n the special medium of filter papers was slow 

 and produced nothing but hyph}e and sclerotia. The same may 

 l)e said of French bean agar ; in this latter case the fungus seemed 

 to remain entirely superficial. Upon oat juice agar growth 

 was very similar to that upon rice agar ; in fact, it is difficult to 

 distinguish between cultures of the same age upon these 

 two media. Upon Lima bean agar the fungus gave rise 

 to a curious red pigment. This developed about three daj^s 

 after infection and slowly spread down the tube following the 

 growth (jf the hyphie (PI. I, Fig. 3). Growth upon maize 

 meal was particularly vigorous, a dense white mycelium being 

 formed in about TJ hours, followed b}' an abundant pro- 

 duction of sclerotia. Here, a<);ain, the jjfrowth of the funcjus 

 is characterised by the production of red pigment in the 

 meal. 



The red pigment is strictly confined to the medium on which 

 it is produced. If an infection is made from a culture upon Lima 

 l^ean agar to glucose agar there is a faint reddening of the 

 gluco.se agar just at the seat of infection, but this speedily 

 dies away and does not spread down the tube. The produc- 

 tion of the pignient is obviously the result of the changed 

 metabolism conditioned l)y the alteration in the nutrient 

 substratum. 



