i53 



The apothecia are either immersed in the thallus or sessile ; the 

 immersed forms can not be said to have thalloid exciples ; but the 

 sessile apothecia are enclosed by a layer of the thallus and should 

 therefore 'be looked upon as having true thalloid exciples. Usually 

 the apothecia are quite small with flattened disks ; in the sessile 

 forms the thalloid margin extends somewhat above the dark disk ; 

 in the immersed apothecia the outline of the disk is quite irregular, 

 reminding one strongly of some species of BuelUa [R. oreina). The 

 hypothecium is colorless and not cortical in structure ; the outer 

 layer of the thalloid exciple is cortical or semicortical, resembling 

 the cortical tissue of Physcia. The spores in the majority of species 

 are dark and typically two-celled as explained in the discussion of 

 the family characters. There are, however, exceptions ; in R. 

 oreina the connecting plasmic bridge is usually wanting ; and it is 

 probable that this species should be classed with the Buellias or 

 separately as Dimelaena oreina as its spore characters, as well as 

 apothecial characters, strongly point to its exclusion from Rinodina. 

 It is not probable that Buellia is as closely related to Rinodina as 

 Reinke and others seem to think ; further study will perhaps 

 demonstrate that discoid sessile apothecia with dark two-celled spores 

 (two cells united by a plasmic bridge) will fully characterize Rinodina 

 and that the forms with distinctly immersed apothecia and two-celled 

 spore, the cells of which are not united by a plasmic thread, should 

 be excluded. The algae of R. oreina are also different from those 

 of the other species which I have examined, being bright green 

 slightly tinged with blue, rather irregular in form, at least more so 

 than in Cystococcus humicola proper ; they resemble more nearly 

 Pleurococcus vulgaris. 



The algae in the remaining undoubted representatives of Rinodina 

 are Cystococcus humicola. They vary in size in the different species, 

 while their general form remains constant. Ectotrophic haustoria 

 are numerous and are closely adherent to the algae ; endotrophic 

 haustoria seem to be comparatively rare. 



There are also multisporous forms of Rinodina (pi. 34, f. 7. ), 

 which according to some authors are included in a distinct genus 

 (Maronea) . 



The Rinodinas are quite common throughout the territory and 

 occur upon rocks and bark, less commonly upon soil and moss. 



