( 234 ) 
of the immediately preceding family, is comparable, in everything but the 
fruticulose thallus. The following brief exposition of the peculiar rela- 
tions of the apothecia to the thallus in a very important part of the group 
before us will illustrate this; and explain as well why I am unable to fol- 
low an eminent lichenographer —to whose vast knowledge of Lichens this 
work has been much indebted—in his estimate of these relations ina 
tropical type. As viewed by Nylander (in Prodr. Fl. N. Gran. p. 6) the 
way in which the apothecia of his Tylophoron (Lindig Herb. N. Gran. n. 
2633, 2653, & Coll. 2, n. 1, 33) are conditioned by the thallus, not‘ only 
excludes it from the present genus, but constitutes it the type of a new 
tribe of his Ser. Epiconioidei, equivalent at once to Caliciei, and to Sphe- 
rophorei ; between which groups he considers it to belong. Itis possible 
indeed, as these tropical lichens (Tylophoron protrudens, and a closely 
related 7. moderatum, Nyl. 7. c.) offer no internal, structural differences 
of account from Acoliwm, as represented by A. tympanellum, &c., that 
such value would not have been attached to their lecanoroid features, 
however striking, had the remarkable Californian species been then known 
to science. In view of these however, it is perhaps not venturesome to 
say that the distinction of Tylophoron is questionable also from the point 
of view of A. tigillare. From this centre of the group a series of forms 
departs, in one direction, towards Calicium ; and this series being the 
only one heretofore (if we except the new <Acolium ocellatum, Koerb. 
Parerg.) represented in Europe, the lecanoroid features of the principal, 
central species have been commonly subordinated. There is notwith- 
standing no doubt that in perhaps the finest conditions of A. tigillare, the 
apothecia occupy regular, more or less hemispherical or conoidal, thalline 
warts (compare Laurer in Sturm D. FI. 2, t. 32) and the question arises, 
if, in the absence of any series of forms explaining and extending this 
peculiar feature of the cited species, lichenographers had reason for subor- 
dinating the difference, they have not now much more for insisting upon 
it, and giving it even place in the generical character, in the presence of 
such series. Irrespective of the discoid spore-mass, the apothecia of 
A. ocellatum (Flot.) Koerb., as of A. Californicum and A. Bolanderi, are 
suggestive even of some Thelotrema ; but these pronounced lecanoroid 
features, which unavoidably condition the descriptions of the lichens 
named, are yet plainly analogous to, and only more marked exhibitions of 
those of A. tigillare. Nor does there appear to be ground for a different 
explanation of Tylophoron, Nyl.; nor in fact for supposing generally, that, 
other structural conditions being equal, the more constant presence of an 
accessory thalline envelope is any less significant or characteristical, in the 
group now before us, than its more constant absence: both modifications 
of structure being already and undeniably represented. It is scarcely 
necessary to add that the former, or lecanoroid exhibition of Acolium, is, 
for us, especially significant of the group, and its rank; and that the 
latter represents rather its deterioration. And these views are not 
