124 GUIDE TO THE STUDY OF LICHENS. 



smooth, colored much as upper surface. Apothecia 

 small, scattered over greater portion of thallus. 

 Disk flattened, black. Spores one, rarely two, 

 light-brown to dark-brown, multilocular, elliptical, 

 71/Lt X 3V 



2. Umhilicaria Pennsylvanica. Thallus medium 

 to large, thin, more or less wavy, margin somewhat 

 torn ; pustules much as in U. papulosa ; dark-gray 

 above ; black and reticulately fitted below. Apothe- 

 cia large, elevated margin. Disk flat, black. Spores 

 68/x, X 27/x, otherwise as in U. papulosa. 



3. Umhilicaria pustulata. Resembles U. papulosa 

 with the exception that the pustules are larger, con- 

 fluent; lower surface more reticulately pitted. Apo- 

 thecia more numerous and showing a tendency to 

 coalesce. Spores as in U. papulosa. 



" According to Linnasus, a beautiful red color may 

 be prepared from this lichen, and it may be converted 

 into ' an exceeding fine black paint ' " — Porcher. 



IV. GRAPHIDACEyE. 



In all probability the family is out of its natural 

 position as here given. The reason that it is placed 

 above the LecideacecB is because it was believed that 

 Rocella should be included in the family, in accord- 

 ance with the views held by Reinke. It is, however, 

 probable that Rocella belongs to the Parmeliacece. 

 If the exclusion is admitted, the Graphidacece are 

 lowly organized lichens, in which the thallus never 

 develops beyond the crustose stage, and hence the 

 family would really be placed before the Caliciacece, 



