74 COLLEMATACEAE 



(a) Spores 2-celled *Dicollema 172 



(b) Spores transeptate, many-celled Collema 171 



(c) Spores muriform Blennothallia 172 



(2) Thallus with a pseudoparenchymatic cortex on one or both sides or 

 pseudoparenchymatic throughout 



(a) Spores transeptate, 3-many-celled 



Leptogiopsis 175 



(b) Spores muriform Leptogium 174 



III. Thallus with Scytonema or Stigonema ; spores colorless 



Subfamily Ephebae 154 



1. Thallus crustose to scaly 



a. Thallus uniform, not corticate 



(1) Spores i-celled Pterygiopsis 157 



(2) Spores 4-celled Petractis 124 



b. Thallus corticate above Porocyphus 157 



2. Thallus dwarf fruticose, much branched, dark 



a. Apothecia sunken in swellings of the thallus 



(1) Spores i-celled; paraphyses present 



Ephebeia 155 



(2) Spores 2-3-celled Ephebe 155 



b. Apothecia superficial 



(1) Thallus without pseudoparenchymatic cortex or central medulla 



(a) Paraphyses capitate, septate Spilonema 154 



(b) Paraphyses filiform, not septate 



Thermutis 154 



(2) Thallus with large-celled pseudoparenchymatic cortex and central medulla 



(a) Cortex of one row of cells; spores 2-celled 



Leptodendriscum 155 



(b) Cortex of several rows 



x. Spores i-celled Leptogidium 156 



y. Spores 2-celled Polychidium 156 



IV. Algae Rivularia ; spores clear Subfamily Lichinae 164 



1. Apothecia disk-form; thallus scaly to granular 



a. Apothecia with proper exciple ; algae horizontal 



Pterygium 165 



b. Apothecia with thalline exciple ; algae erect 



Steinera 166 



2. Apothecia almost perithecioid ; thallus dwarf fruticose 



a. Algae in the middle of the thallus and parallel with the long axis of the 



branches Lichinodium 166 



b. Algae absent from the middle but marginal beneath the cortex 



(1) Algae parallel with the long axis of the branches 



Lichina 167 



(2) Algae perpendicular to the long axis 



(a) Paraphyses present Lichinella 166 



(b) Paraphyses absent Homopsella 167 



