206 NEW SUGARCANE DISEASES 



drawn 48 hours after sowing. The fungus can be readily culti- 

 vated on most ordinary media, but the spores formed in culture 

 are usually smaller than those from the host plant. The 

 following inoculations were made with pure cultures on nutrient 

 agar. 



In January 1909, 8 leaves of growing sugarcane were inocu- 

 lated on the upper surface with a suspension of spores and my- 

 celium, a drop of which was placed on each leaf and covered with 

 damp, sterile cotton-wool. The leaf was not injured in any wa}'. 

 After 6 days, o of the inoculations were found to have succeeded, 

 a red spot developing at the inoculated point and eventually giv- 

 ing rise to a typical infection. The other 5 and the controls 

 showed no change. A second series was made at the same time 

 on young healthy shoots brought into the laboratory. On these 

 6 inoculations were made, 3 being kept damp with cotton- wool 

 and 3 by covering with bell-jars. The latter showed evident 

 signs of infection in 2 days, but only I of the former succeeded 

 and the spot was not visible until the fourth day. A month 

 later 9 more inoculations were made on healthy shoots kept 

 under bell-jars, all of which succeeded. One showed reddening 

 in 24 hours, 4 more were visible in 3 days, and all were well 

 marked in 5 days. A little later, 21 more inoculations were made 

 in a similar manner to those of the last series. All succeeded 

 well. 



The microscopic examination of the inoculated leaves showed 

 that penetration occurred directly into the epidermal cells 

 (PI. VI, Fig. 3). The infecting hypha swells up slightly in 

 close contact with the cuticle and a narrow tube arises from the 

 swollen portion and pierces the wall. As soon as the cell cavity 

 is entered, the hypha swells up again and becomes freely septate, 

 often forming a small mass of pseudo-parenchymatous cells. 

 From this, branches pass to the deeper cells, and others approach 

 the surface to form new stromata. The pressure exerted by these 

 epidermal stromata is sometimes enough to rupture the outer 

 wall before reproduction begins. The fructifications are usually 

 confined to the quite dead central part of the spot. 



