194 NEAY SUGARCANE DISEASES 



largest up to 33 m in diameter, at tirst h3'aline but later slightly 

 coloured. They frequeiuly separate from the mycelium when 

 inature, and may be found lying singly or in short chairis inter- 

 mingled with the hypha3. They germinate in water by an 

 outo-rowth of the endospore. The nodular swellings on the 

 smaller hyphtu seem to be of the same category, but do not 

 usually become detached ; they often give oft' fine branches after 

 reaching maturity. In many cultures no other spore form was 

 found. In several, however, a pycnidial stage developed, and this 

 stage was subsequently found on the surface of old canes which 

 had been killed by the disease. 



When pycnidia were formed, they began to appear in about 

 3 weeks after sowing the tubes, as fine blackish dots immersed in 

 the white mycelium. These grew to form prominent black 

 nodules, which, under the microscope, were found to consist of 

 stromatic tissue with one or more sporiferous loculi entirely 

 immersed in the stroma. 



The stromata are leathery, roundish-conical, about 1 to 

 2 mm. in diameter, and consist of an outer portion of brown, 

 fibrous tissue, composed of closely woven hypha3, and an inner, 

 bounding the loculi, of dark brown pseudo-parenchyma, many 

 layers deep. Sometimes bands of the fibrous tissue separate the 

 loculi, each cavity then having its separate investment of pseudo- 

 parenchyma (PI. Ill, Fig. I), in others the whole centre portion 

 of the stroma is cellular and the cavities have no distinct walls, 

 except the lighter coloured layers from which the spore stalks 

 arise. The cells of the pseudo-parenchyma are distinct, angular, 

 isodiametric in the deeper layers, but becoming more elongated as 

 the hymenium is approached, with un thickened but deeply pig- 

 mented walls and oily contents, and measuring up to 10 m in 

 diameter. The colour gradually becomes lighter towards the 

 spore-bearing surface. 



The p3'cnidial loculi are deeply sunken in the stroma, very 

 irregular in shape, and often communicate with one another by 

 narrow passages. Every stage may be found between stromata 

 with a single loculus, through such cases as shown in PI. Ill, 



