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lichens; but they are none the less explainable from our present point of 
view. An always included hymenium may be called nucleiform, but is 
not on that account necessarily Verrucariaceous; and there is nothing in 
the hymenium of Pertusaria, and the structure immediately conditioning 
it, to exclude it from Lecanorine affinity. Direct evidence to such affin- 
ity is afforded moreover by the fact that species slip back, not seldom, 
into scutelleform states; in one at least of which the normal apothecium 
of the sub-family last considered is so distinctly presented, that the 
lichen may almost pass, and is indeed claimed, at once, for a Lecanora, 
and a Pertusaria. 
Scarcely less clear is it that if Pertusaria thus reverts to Lecanora, 
the latter, for its part, is not-without anomalies anticipatory of Pertusa- 
ria. This is especially seen in the distinguished cluster of Lecanore 
which of all others most nearly approaches, in the spores, to the group 
now before us. The fruit of L. tartarea, v. pertusarioides, Th. Fr., is de- 
scribed (Lich. Arct. p. 100) as rounded and flattened warts, impressed 
above with now as many as ten, minute, yellowish-rosecoloured disks. 
And L. pallescens, v. rosella, Tuckerm. herb., is a similarly irregular, 
American lichen, in which what should be the disk of a simple apothe- 
cium is divided, by processes from the interior of the margin, meeting at 
the centre from which they appear to radiate, into from five to fourteen, 
small, at first ovate disks, passing at length into mere cracks between 
the very numerous processes; and these last becoming thus predominant 
at the expense of the hymenium, the Pertusarieine type is not seldom, or 
doubtfully suggested. 
It is then, in this view, the lecanorine hypothecium —not rarely 
extended upwards into a margin in the Hulecanorei, as well as in Gya- 
lecta — which explains the now evident inner border of lecanoroid Pertu- 
sarie ; and furnishes, in the compound species, at once the dissepiments 
which part, and the common tissue which envelopes, and even (in 
P. Wulfenii) finally encircles, with an elevated, blackening ring, the 
clustered hymenia. 
But Pertusaria touches Philyctis and Thelotrema, on the one hand, 
almost as clearly as Lecanora, on the other; and unites thus the now 
almost Parmeliine Hzlecanorei and the sometimes too discrepant Urceo- 
lariei in one and the same natural family. It is yet hardly to be ques- 
tioned that the group stands in nearest relations to Ewlecanorei; and 
the spores, instead of at once removing it, as Phlyctis, &c., are removed, 
from the line of direct analogy with Parmelia and Lecanora, are in this 
line, and offer, though the ultimate differentiation be not reached, the most 
remarkable known expression of the Lecanorine spore-type ; foreshadowed. 
only in L. tartarea, &c. Nylander’s recent discovery of a Pertusarieine 
type (Varicellaria, Nyl.) in which the second stage in the evolution of the 
colourless spore is exhibited, suggests indeed the possible occurrence of 
other types, displaying its further development. But Pertusaria leuco- 
