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U. atropruinosa,’ and suggested that it might hereafter appear that the 
natural position of Umbilicaria were between the other two genera 
named. ‘Est omnino, he adds, four years later (Fl. Scan. p. 280) ‘ex hac 
grege’ (Graphideis) ‘removendum, et inter Stictas et Parmelias inserendum.? 
But Flotow (1. c.) first gave definite expression to this conception. He 
declared the apothecia of the Umbilicariei to be ‘imperfect scutelle’ (wn- 
volistindige Scutellen) and.by adding to it the exotic, ‘umbilicate Par- 
melie’ (Omphalodium, M. and Flot., Koerb.) left no longer any ground to 
question its position. Koerber (Syst. p. 92) maintains the same view, 
restricting however Omphalodium to the exotic species; and Nylander, 
who does not admit the latter genus as distinct from Parmelia, agrees in 
the Parmeliaceous character of Umbilicaria. There seems to be no rea- 
son to doubt that the two remarkable lichens brought together in Om- 
phalodium (Sticta hottentotta, Ach., and Parmelia Pisacomensis (M. and 
Flot.,) Nyl.) satisfactorily mediate between the Parmeliei and Umbilica- 
ria, to whichever family we refer them; but it is perhaps less easy, on 
the whole (nothwithstanding the evidence of the spermogones, Nyl. Syn. 
p. 399) to reconcile them with the former than with the latter, from which 
(Umbilicarie’) indeed, P. Pisacomensis might be regarded as chiefly dif- 
fering in being a less abnormal member of the family. PP. hottentotta is 
at first sight more difficult, exhibiting as it does the habit as well as the 
coloration of many Sticte; the spores however are in fact by no means 
alien to certain conditions of those of Umbilicaria, and the plant may be 
conceived as occupying a place in the Umbilicariei immediately analogous 
with Parmelia in the Parmeliei. In this view stress is of course laid on 
the (often stalk-like) disk, by which these plants are attached to the 
rock-surface on which they grow, as affording the by far most important 
of their thalline characters. The curious fringe of greenish-glaucescent, 
at length whitish, laciniate, physcioid lobules which (scarcely described 
perhaps except by Turner and Borrer, Lich. Brit. p. 217, 225, ete.) bor- 
ders the disk of attachment in Umbilicaria is observable also, as respects 
its general features (though not as respects colour) in the fragment be- 
fore me of Omphalodium Pisacomense; but in the herein as otherwise 
discrepant O. hottentottum, this fringe is made up of crowded, teretish 
branchlets, to be compared rather with the similar outgrowth (‘ fibrille,’ 
Hoffm.) in Sticta filix, and explained doubtless by the root-like fibres 
(rhizine fasciculate, Nyl.) of other Sticte. It is also noteworthy that 
the disk of the at length blackening apothecia of O. Pisacomense is not 
seldom papillated, much as occurs also in the otherwise not always dis- 
similar shields of Umbilicaria Pennsylvanica, and exactly as in U. pustu- 
lata, v. papillata, Hampe, from the Cape of Good Hope, as if the first- 
named might itself in time become proliferous; and that Delise (Hist. 
Stict. p. 136) has described a variety of O. hottentottum, ‘ disco umbili- 
cato nigricante,’ (Stict. p. 135). 
But it is not, as has already appeared, with Parmelia alone that the 
