(184) 
The importance of this group is not to be measured by its size. While 
evidently Lecanorine, as respects the principal species, it may be said to 
take hold of both Gyalecta and Thelotrema; and thus to harmonize 
otherwise discordant, Biatoroid, and even Verrucarieform conditions with 
the Parmeliaceous type. Nor are its relations to Pertusaria entirely 
without significance; the fruit of Urceolaria tending readily to become 
compound, when it is not difficult to select samples (at least in the con- 
dition of U. cinereo-cesia published in Wright Lich. Cub. n. 161) not 
distantly suggesting that of the genus first-named. If we consider the 
best known forms, we find the first (U. ocellata) receding towards Leca- 
nora, —the finally inflexed, but more often obscure margin of the proper 
exciple being coloured like the thallus. The second (U. scruposa) offers 
at once the type of the group, and its point of nearest affinity to Thelo- 
trema ; and both thalline and proper exciple play an important part in 
its history. While in the third (U. actinostoma) the proper exciple con- 
stitutes the apothecium, and remaining closed (Koerber’s remarks on his 
U. clausa, Parerg. p. 105, should be compared here) the lichen looks not 
unlike a Gyalecta, and differs in fact but little from some species of that 
genus, even in character. When the proper exciple of Thelotrema black- 
ens, there may remain little but the often evanescent veil to distinguish 
it from Urceolaria ; and T. Santense, Tuck. Obs. Lich. 1. c. 5, p. 406, is a 
conspicuous example, of which T. compunctum, Nyl. (Urceolaria, Ach.) 
and with little doubt Urceolaria thelotremoides, Mass. Ric. p. 35, furnish 
others, of such Urceolariiform species. Massalongo says indeed of the 
last-named, that the species of Urceolaria proper differ from it in no 
single generical character; which may be true, without our being able 
to take a tropical bark-lichen out of its own series of affinities, and refer 
it to a northern, saxicoline group. 
As the centre of a sub-family especially conditioned by the spores, it 
should not surprise us to find in Urceolaria something looking towards 
an explanation of the discrepancies from the prevailing spore-type, occur- 
ring in some more recedent members of the group. I venture to think 
that the development of the Urceolaria-spore, taken in its full extent (as 
from colourless, and bi-quadrilocular, it becomes muriform-plurilocular, 
and brown) is thus instructive, in the case of Gyalecta. And it is cer- 
tainly suggestive, as respects Thelotrema, that the multiform differentia- 
tion of the spores of this genus is conceivable, at least in its larger fea- 
tures, as a varied exhibition, in detail, of the progressive changes in the 
evolution of the Urceolariine type. 
The five or six described species are all saxicoline or terricoline, and 
mainly northern. U. scruposa passes indeed southward to Polynesia 
(Nyl. Enum. Gén.) and is very nearly akin to one of the two tropical 
forms (U. cinereo-cesia, Ach.) if indeed the latter (as compare Nyl. in 
Prodr. Fl. N. Gran. p. 35) be really distinguishable from it. Of the 
best-determined, European conditions, all are found here except U. ocel- 
