162 Ustulina Zoiiata (Lev.) Sacc. on Hevea Brasiliensis 



apices of hyaline liyphae compacted to form a smooth surface. They 

 measure four microns by two. 



The perithecial openings can be observed as minute black spots almost 

 immediately after the disappearance of the conidial layer. By this time 

 the black zone is continuous, and the spore chambers are developed just 

 below this zone in the more loosely compacted tissue. The asci are numer- 

 ous, with paraphyses. The ascospores, when first dehmited from the 

 remainder of the protoplasm in the ascus, are hyaline, with no special 

 contents. Later, they darken, become almost black, with two or three 

 oil drops. They are slightly curved, inequilateral and lie to end in the 

 ascus. The ascospores are 28-32 microns by 7-10 microns. They exude 

 through the openings of the perithecia under moist conditions, looking 

 like small drops of ink. When the amount of moisture fails, the exuded 

 spore masses spread out over the surface, resembling black patches of 

 dust surrounding the perithecial openings. Only on one occasion did the 

 ascospores germinate readily ; these were obtained immediately after ex- 

 trusion from a fructification developed in the laboratory. Placed in 

 potato mush agar in damp chambers they germinated in twenty-four 

 hours, several germ tubes being put out along the side of the spore, none 

 from the ends. The tubes grow vigorously and branch profusely. 



The conidia germinate more easily, but do not produce a copious 

 mycelium on potato mush agar in damp chambers. Conidia placed 

 directly on slants, however, produce just as vigorous a mycelium as is 

 formed from sowings of ascospores. Cultures are not easy to obtain from 

 spores developed in the field, though the fungus can nearly always be 

 obtained in pure culture from the black lines formed in the diseased 

 tissue. 



There is as much variety in the form of the specimens from Malaya as 

 in those from Ceylon described by Fetch. There is a solitary stalked form 

 (PI. V, fig. 11), the conidial layer being produced only on the top and con- 

 tinued a short distance down the sides. In some cases, these stalked forms 

 may be aggregated to form a compact plate, the heads of the stalks becom- 

 ing hexagonal in shape owing to mutual pressure. This approximates to 

 the typical Kretschmaria form, the common Kretschmaria coenopus (Fr.) 

 closely resembling this form of U. zonata, but the ascospores of the latter 

 are much larger. There is another form which has not yet been found to 

 produce spores; this closely resembles a foliose lichen (PI. VI, fig. 14). 

 PI. V, fig. 10 shows a photograph of a fructification vaih. the lichenoid type 

 at the edges, gradually passing into the plate-Uke form with hexagonal 

 heads; the commoner flat plate-like form was growing up from beneath 



