82 UMBILICAKIA. 



XIII. UMBILICAKIA, Hoffm. 



Apothecia sub-scutellseform, variously difform, blackened, 

 destitute of gonidia,- for tbe most part at length lirellose- 

 proliferous. Spores ellipsoid, from simple at length grauu- 

 lose; or, more rarely, muriform-multilocular, fuscescent. 

 Spermatia oblong 5 on multi-articulate sterigmas. Thallus 



as above. The anatomy of the thallus is largely illustrated 



by Schwendener, I. c. 3, pp. 150, 179 j t. 8, /. 15-17; t. 10, 



/. 10-13. Neither of the attempts heretofore made to 



divide this natural genus into two, can be called satisfactory. 

 Acharius soon gave up his distinction based on the degree 

 of external, atypical change in the apothecia; and if 

 Nylander has indicated recently, with emphasis (Flora 

 Eatisb. 1875, p. 303) that this external change, so obvious 

 in the descent from V. pustulata to most species of our first 

 section, is accompanied by a gradual modification or degen- 

 eration of the tissues of the same organs, we may admit the 

 fact, embarrassed though it be by the difficult association of 

 U. anthradna and U. pustulata to form the new genus 

 Umbilicaria, Nyl., but hardly the inference that he draws 

 from it. It is impossible, too, any longer to lay that stress 

 on the spore differences which Fee, and Flotow, and most 

 recent writers have attempted. And Schweudeuer has him- 

 self admitted the difficulties of his characterization of Gyro- 

 jphora and Umbilicaria, from the thalline characters alone. 

 The general structure of the thallus offers no prominent 

 differences from that of Parmelia and Physcia ; and the 

 distinction of the group, marked as it is, may be said to 

 rest on its peculiar coloration, taken in connection with the 

 deficiency of gonidia in, and the denigration, and abnormal 

 development of, its fruit ; and the manner of attachment of 

 the thallus to the substrate. In some states of the highest 

 -expressions of Umbilicaria, as U. pustulata v. papillata 

 Hamp., a Cape of Good Hope lichen, there is now indeed 

 nothing external which may not be taken for Parmelieine, 

 the thalline exciple agreeing entirely in colour with the 

 pale greenish-brown thallus ; but in a full view of the fruit 



