128 



DISCOMYCETES 



[CH. 



Rhizinaceae 



The Rhizinaceae are characterized by their unstalked fructification, and 

 include the genera Rhizina and Sphaerosoma. 



Rhizina has a flattened, crust-Hke ascophore, more or less concave below, 

 and attached to the soil by root-like strands of mycelium. The asci cover 

 the upper surface. 



Rhizina inflata occurs in this country only as a saprophyte, growing 

 on soil, but in both France and Germany it has been found to attack 

 conifers. The disease, known as ring' disease, or root fungus, extends from 

 a centre, infecting one plant after another and causing them to lose their 

 needles and die. The mycelium ramifies in the intercellular spaces of 

 the cortex, and within as well as between the cells of the bast, so that the 

 sieve-tubes are completely filled. It forms also masses of pseudoparenchyma 

 between the dead and diseased tissues of the host. 



The development of the ascocarp has been studied in R. tcndidata where 

 Fitzpatrick found a long, multicellular archicarp recalling that of some of 

 the Ascobolaceae. He regards the terminal cell or cells as a trichogyne 

 but there is no evidence that normal fertilization ever takes place or that 

 male organs are ever developed. In due course, the central cells become 

 continuous through large pores, and give rise to ascogenous hyphae into 

 which the nuclei pass. Fitzpatrick observed paired nuclei in the oogonial 

 region and in the ascogenous hyphae, and infers that nuclear association 

 occurs in the archicarp, but that there is only one fusion, that in the ascus. 



Fig. 88. Sphaerosoma Janczewikianum Roup. ; apothecium showing 

 oogonial cell, x 70 ; after Rouppert. 



