The Fungus present in Lunularia cruciata {L.) Dum. 85 



veloped near the thallus. Several hyphae may pass up one 

 rhizoid, as many as five ha\dng been observed. Cross walls are 

 present at rather long intervals and ladder-hke fusions fre- 

 quently occur (Fig. 2). The fungus branches as soon as it reaches 

 the thallus (Fig. i), ramifies in it, and, in hea\ily infected plants, 

 mav extend to \\ithin 2-3 mm. from the growing point. 



In slightly infected plants isolated patches of infected cells 

 occur. These result from the entrance of hyphae into the thallus 

 through a rhizoid immediately beneath the infected tissue. The 

 appearance of the fungus is exactly similar to that in more 

 heavily infected material. 



Young plants, not more than 2-3 mm. in length, and de- 

 veloped from gemmae, were found to be hea\T.ly infected and 

 the hyphae were similar to those in mature plants. In transverse 

 section of such plants the fungus is seen to occupy the whole 

 of the central portion, in some cases reaching to the base of the 

 assimilating tissue. 



Mature plants of Lunularia are normally from 20-25 cells 

 in thickness in the thickened central portion. The lowest three 

 or four layers of cells contain starch grains and are not occupied 

 by the fungus except where hyphae are entering through a 

 rhizoid. With the exception of the oil cells the six to nine layers 

 of cells immediately above contain the fungus. From the re- 

 maining six to ten layers of cells of the ventral tissue the fungus 

 is absent (Fig. i). In very hea\dly infected plants, the infected 

 zone may reach the base of the assimilating tissue at the wings 

 of the midrib. The assimilating tissue is ne\-er entered by the 

 fungus even after the plant is dead. The fungus does not occur 

 among the gemmae. No reproductive organs of the fungus have 

 been found on the material examined. 



Behaviour of the Fungus in the Cells 

 OF the Thallus. 



When sections of infected plants are examined under a high 

 power magnification numerous hyphae are \'isible, passing from 

 cell to cell. These are relatively massive, measuring from 3-5- 

 7-5^ in diameter, \\dth granular contents, and are septate at 

 long and irregular intervals. The mode of growiih of these 

 hyphae is normally parallel with the lower surface of the thallus. 

 Apparently the cell walls of the liverwort are not injured by the 

 fungus except at the point of penetration. The hyphae usually 

 become constricted before piercing the cell-wall (Fig. 3), so that 

 it is probable that penetration is effected by mechanical means, 

 and that the cell-wall is not dissolved by a cellulose destroying 

 enzyme. 



