KEY TO THE ARRANGEMENT. 



pulp, amidst branched medullary filaments. Apothecia 

 normally scutellseform ; sometimes, in the lower groups, 

 persistently globose. 



25. PYRENOPSIS. Apothecia depressed-globose, urceolate, 



or DOW at length open. Spores ovoid-ellipsoid, simple 

 or bilocular, decelerate. Thallus granulose. Gonimia 

 in clusters; or now in chains. 



26. OMPHALARIA. Apothecia sub -globose, immersed 



more or less in the thallus, or finally superficial, and 

 explicate. Spores ellipsoid, simple, decolorate. Thal- 

 lus fruticulose, or more commonly foliaceous, attached 

 to the substrate, at only one point. Gonimia in 

 clusters ; or rarely in chains. 



27. COLLEMA. Apothecia scutellseform. Spores ovoid- 



ellipsoid, either simple, or becoming fusiform, and bi- 

 plurilocular, or most commonly muriform-plurilocular, 

 scarcely coloured. Thallus foliaceous, very rarely 

 fruticulose ; mostly dark-green ; cortical layer mostly 

 indistinct ; gonimia almost always concatenate ; 

 medullary filaments conspicuous. 



28. LEPTOGIUM. Apothecia scutellaeform, or zeorine; or 



biatorine. Spores ovoid-ellipsoid, either simple, or 

 becoming fusiform and bi-plurilocular, or, most often, 

 muriform-plurilocular, scarcely coloured. Thallus 

 foliaceous, or rarely fruticulose, mostly lead-coloured ; 

 cortical layer distinctly parenchymatous ; gonimia 

 and medullary filaments as in Collema. 



29. HYDROTHYRIA. Apothecia biatorine. Spores fusi- 



form, quadrilocular, uncoloured. Thallus foliaceous, 

 lead-coloured ; cortical layer distinct, as in Leptogium ; 

 gonimia disposed, in very short chains, between the 

 compact medullary layer, and the cortical. 



