246 CLASS ASCOMYCETEAE 



Thallus fruticose, "proper exciple" present. California. 



Family Roccellaceae 

 Cortical hyphae longitudinal. Dendrographa 



Cortical hyphae transverse. 



Spores hyaline. Roccella 



Spores brown. Schizopelte 



Apothecia more or less round or cup-like. 

 Host algae Myxophyceae. 



Thallus taking its form from that of the host. 



Thallus squamulose to foUose; on Nostoc. Family Collemaceae 

 Spermatia produced within thallus. Collemodes 



Spermatia produced in spermogonia opening externally. 



Ascospores only transversely septate. Synechoblastus 



Ascospores both transversely and longitudinally septate. 

 Definite cortex lacking. Collema 



Thin definite cortex present. Leptogmm 



Algal host Scytonema or Stigonema. Family Ephebaceae 



Seven small genera in the U.S. 

 Thallus rarely tak'ng its form from that of the algal host. 

 Thallus large, plainly foliose. 



Apothecia without distinct exciple. Family Peltigeraceae 



Thallus with cortex above only; apothecium on under surface of 



the thallus lobes. Nephroma 



Thallus with cortex above and below; apothecia on upper surface. 

 Ascospores hyaline. Peltigera 



Ascospores brownish to brown. Solorina 



Apothecia with distinct exciple. Family Stictaceae 



Single genus in the U.S. Sticta 



Thallus small, crustose to somewhat foliose or dwarf fruticose. 



Several small families, mostly growing on soil or rocks: Pyrenop- 

 sidaceae, Lichinaceae, Heppiaceae, Pannariaceae. 

 Host algae Chlorophyceae.^ 



Apothecia without exciple or this only rudimentary (fairly well developed 

 in Lecanactis) . 

 Thallus crustose, ascospores nonseptate or transversely septate. 



Family Lecanactidaceae 

 Three small genera, mostly on trees, but some species on rocks or 

 soil. Not widely spread over the U.S. 

 Thallus crustose, ascospores transversely and longitudintJly septate. 



Family Ectolechiaceae 

 Only one species, of the genus Lopadiopsis, in the U.S. ^ 



Apothecia with well-developed exciple. 



Both proper and thalloid exciple present, the latter sometimes dis- 

 appearing. 

 Apothecia more or less deeply immersed in the thallus. 



Family Thelotremaceae 

 Five genera in the U.S., mostly Southern. 

 Apothecia superficial or not deeply immersed. 



Proper exciple dark. Family Diploschistaceae 



' A few species of the foregoing families that are mostly parasitic on Myxophyceae 

 have Chlorophyceae for their host; see especially Peltigeraceae and Stictaceae. 



