PATHOLOGY OF YOUNG TREES AND SEEDLINGS. 227 



proportion of the facts upon which the following communication 

 is based. 



The genus Rosellinia includes a large number of species found 

 growing on plants, and, although the majority are saprophytes 

 developing only on dead tissues, a few are parasites and cause 

 serious plant diseases. The genus is placed in the Pyrenomycetes, 

 a large subdivision of the Ascomycetes characterised by the 

 production of closed fructifications, the perithecia, containing 

 the asci in which the ascospores are produced. In the 

 Sphaeriaceae, the family to which Roselli7iia belongs, the 

 perithecia are small, black, pear-shaped or globose structures, 

 and are produced on the surface of or slightly embedded in 

 the substratum, each one being formed quite independently. 



The parasitic species of the genus have a common character, 

 which has a very important bearing on the type of disease 

 produced by them. Long strands or filaments made up of a 

 number of longitudinally arranged hyphae are produced, which 

 not only penetrate the stem and root of the diseased plant, but 

 spread through the soil and over the substratum and bring 

 about the infection of other plants in the vicinity. 



The serious nature of the diseases produced depends largely 

 on this character, for distribution by means of the mycelial 

 strands is rapid under suitable conditions, and it is a difficult 

 matter to exterminate the fungus in the soil when the latter 

 has become thoroughly infected. 



Rosellinia quercina, which attacks young oak trees, was first 

 described by Hartig^ in Germany in 1880. The first sign of 

 the disease is the withering and death of the upper leaves, 

 and soon the lower leaves are affected in the same way and 

 the plant dies. If the root of a dead plant is examined it is 

 found to be more or less covered with a whitish mycelium, 

 and this often extends up to the stem, and when the plant 

 is in the ground, spreads over the surface of the soil. Later 

 on the mycelium becomes brown, and small black sclerotia 

 are found on the surface of the root. Conidia, borne on slender 

 conidiophores, are produced on the collar of the plant near 

 the surface of the soil. Finally the globose, black perithecia 

 are formed on the dense mycelium covering the lower part of 

 the dead plant. 



1 " Untersuchungen a.d. forstbotanischen Institut zu Miinchen,"' I., 1880, 

 p. I. 



