CORRIGENDA. 
Page 3, line 1, for 2 read 1. 
P.7. DACTYLINA. The spermogones and spermatia of D. arctica, as 
described by Lindsay (on Spermogones, &e., Trans. Edinb. v. 22, p. 133; t. 6, 
f. 23) approach nearly to those of D. madreporiformis (Ibid. p. 132) and are 
admitted to do so by Nylander (Recogn. Ramat. p. 77, 1870) though the latter 
prefers, in case the two shall hereafter be admitted by him to be congenerical, to 
bring them together, as Sir W. J. Hooker has already done, in an emended 
Dufourea. Upon this the present writer’s remarks (Obs. Lich. 1. c. 5, p. 396) may 
be compared. The important discovery, by Dr. J. Miiller (Flora, 1870, p. 321) of 
apothecia in the heretofore always reckoned sterile D. madreporiformis should 
seem however to leave no doubt remaining of the very close affinity of this lichen 
to D. ramulosa (upon which compare the descriptions in Obs. Lich., above cited) 
and the spores of the former are not distinguishable from those of Cetraria ; with 
which in fact Miller regards the plant as best associable. This view appears cer- 
tainly to have much to commend it; but Nylander (Flora, 1871, p. 298) prefers 
rather to insist on the affinity of our lichens in question to Evernia, and Parmelia. 
A single, young, lateral apothecium, entirely agreeing with similarly situated 
ones of D. ramulosa, has occurred to me in specimens of D. madreporiformis 
from the Rocky Mountains (Dr. Parry) and the mature fruit may therefore be 
looked for there.——The species last named was mistakenly considered by Acha- 
rius to be the same with Lichen madreporiformis of Wulfen ; upon which, as upon 
the synonymy in general, compare especially Miiller, 1. ¢. 
P. 10, and pp. 22-23. CETRARIA. The remark is made, at the place first 
cited, that the evidence of the spermogones appears to be scarcely sufficient to 
refer beyond doubt Parmelia Fendleri to Cetraria ; and that the reference to the 
same genus of P. Iuhlunensis, may possibly also be questionable. The recent 
observation of Dr. Th. Fries (Lich. Scand. p. 110, 1871) that the spermatia of 
Parmelia aleurites, Ach., do not accord, as asserted by Nylander, with those of 
P. hyperopta, Ach., but rather with those of certain species of Cetraria, led me 
however to a renewed study of the lichen first named, which I had already, under 
another name, once referred (Syn. Lich. N. Eng. p. 16, 1848) to Cetraria. The 
result was that I found my own, American specimens affording spermatia like 
those described by Fries; and that I reached at length the better view of these 
lichens now to be set down. Cetraria aleurites, Th. Fr., appears then to be asso- 
ciable, in general, at once with the species next to follow, as especially with 
C. aurescens, Tuckerm.; and to differ, to this extent, from P’armelia. Acharius’s 
description of his Parmelia aleurites (Z. U.) seems moreover to point, not to what 
was afterwards called P. hyperopta (Ach. Syn.) but to what Dr. Fries intends by 
Cetraria aleurites: and Dickson’s published specimen (from ‘old pales, Croft cas- 
tle, Hereford’!) which is cited by Acharius, is certainly the same plant; as are 
