2oS 



IiXTRODUCTION TO THE STUDY OF FUNGI 



Euryachwa the stroma is broadly etfused and puiictulate, whilst 

 in Homoxlcjia the stroma is plane or hemispherical, and the 



species are parasitic upon 

 Lichens. In Illiupogyaphus 

 the stroma is elongated and 

 linear, suggesting a resem- 

 blance to some Hysteriaceous 

 perithecia. Species of Phyl- 

 lachora are common on cori- 

 aceous leaves in tropical coun- 

 tries, and are sometimes 

 difficult to distinguish at 

 first from some of the PJiy- 

 tisriioideac. In common with 

 the latter the stroma is often 

 present for some time before 

 the fructification is developed, 

 hence they are often met with 

 in a sterile condition. 



The subfamily Rhytis- 

 moideae is included by some 

 on account of the mode of 



Flu. 97. — Ihddiiiia, globose stroma and 

 sectiou. Oard. Chron. 



authors with the Discomycdea 

 dehiscence, which is usually by gaping fissures, so that the 

 hymenium is more or less exposed ; but this dehiscence does 

 not take place until the sporidia are 

 fully mature, and sometimes not until 

 disintegration has commenced. In 

 external appearance the species arc 

 very similar to Phyllachora and Eury- 

 acliora, and yet in texture of the 

 stroma, and often in the fructification, 

 appear to be more closely allied to 

 the Dothidcaceae than to any family 

 of the Discomyccteae. Practically, the 

 only genus is IlhyUsma, for the sporidia 

 of so many described species are 

 unknown that no proposals have been 

 possible to divide them into genera based upon the fructifi- 

 cation. Such a species as Rhytisma accrinum, which is common 



Fig. 98.— Globose stroma of 

 Jfl/2}oxi/lo)i, with asci and 

 si:)oridia. 



