132 



3. Section of apothecium. 



a, thecium ; b and c, hypothecium ; d, algal layer (often wanting) ; e, 

 loose network of hyphae. 



4. Section of thallus. 



5. Paraphyses and spore-sac with spores. 



6. Spores. 



7. Algal chain ; a, pyrenoid bodies. 



3. Biatora Fr. Lich. Dian. Nov. 1817. 



Authors have made this genus the dumping ground for all 

 lichens which have the faintest macroscopical resemblance to the 

 typical species. As a result the genus grew to such enormous pro- 

 portions that it became impossible for a beginner in systematic lichen- 

 ology to understand it at' all. This I have endeavored to correct by 

 isolating from Biatora the following genera : Biatorella, Biato- 

 ridium, Biatorina, Bilimbia, Bacidea and Psora, which simplifies 

 the work of classification very materially and tends to prevent con- 

 fusion, which is certainly desirable in our present arrangements. 



The genus is characterized by a crustaceous thallus and simple 

 colorless elliptical spores. The thallus, however, varies from typi- 

 cally crustaceous to warty and minutely foliose, merging into the 

 foliose forms of Psora. I have, retained under Biatora all those 

 forms in which the foliose character of the thallus is not sufficiently 

 marked to be readily determined ; in some species it is evident that 

 the thallus varies from warty to faintly foliose and could, therefore, 

 not be classed as foliose. Biatora is also liable to be confused with 

 Lecidea, for we have the same spore-characters in both ; the only 

 difference is the dark hypothecium in the latter genus, but on care- 

 ful examination it is, however, found that this character is not reli- 

 able, since we have a gradual series from colorless hypothecia in 

 Biatora to dark hypothecia in Lecidea. The general characters of 

 the thallus are the same in both genera ; the algae are Cystococcus 

 humicola. 



The apothecia are of medium size, disk usually convex, some- 

 times flattened ; the excipular margin is rarely somewhat elevated. 

 The apothecia are also more or less immersed in the thallus, but not 

 sufficiently to be characteristic ; the color of the epithecium varies 

 from light brown to dark and black. - 



Biatora is evidently closely related to Parmelia, as indicated by 

 its apothecial and spore-characters. In general it may also be stated 



