Tht F ungus present in Liinularia cruciata (L.) Diim. 83 



Plants growing on a decayed tree-stump in Leigh Woods, 

 Somerset, were found to be hea\-ily infected, but others groNving 

 in close proximity to them on a steep bank were quite free from 

 the fungus. Some plants at a short distance from these on a 

 gravellv path were shghtly infected, but in others of the same 

 group the fungus was absent. Plants growing on the ground 

 amons: mosses in Blaize Castle Woods, Gloucestershire, were 

 quite free from infection. Small plants of Lunularia of brownish 

 colour from a vard of the Bristol Musemn were hea\"ily infected ; 

 the substratum upon which these were growing consisted chiefly 

 of the dead remains of plants of the same species. 



The hvdrogen ion concentrations of several samples of soil 

 upon which Lunularia was growing were measured by the 

 colorimetiic method, the experimental procedure for obtaining 

 the soil solution used being originally described by Golas and 

 quoted by Cavers (19 14). AU the soils thus tested were black 

 loamy soils. The figures for the Pn values obtained were as 

 follows : 



Material 



Method of 



obtaining soil 



solQtion 



Indicatioii 



Ph value 



The presence or absence of infection has apparently no con- 

 nection with the degree of acidity or alkalinity- of the soil. 

 Sections of the thallus when tested showed that the Ph value 

 of both infected and iminfected tissue were about 6-4. 



The presence or absence of the tongus in Lunularia is appa- 

 rentlv not determined by any en\-ironmental factor and its 

 occurrence appears to be merely by chance. 



Distribution of the Fungus ix the Plant. 



In longitudinal sections cut through the midrib of well- 

 infected plants, the region occupied by the fungus is conspicuous 

 as a ver\" detiriite zone of brownish cells parallel to the lower 

 surface, and in sharp contrast to the remainiag colourless cells 

 of the ventral tissue (Fig. i). In transverse sections this fungus 

 region is seen to consist of a single strand occupying a con- 

 siderable portion of the ventral tissue of the midrib. 



6—2 



