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the North American lichen; both L. phyllocarpum and L. bullatum being 
Mexican plants (Nyl.) and the former at least most closely approached by 
some of the Texan specimens of the present; as others exhibit a thallus 
not appreciably distinguishable from that of the original L. Javanicum. 
——17. L. Burgessii (Lightf.) Mont. Trunks, White Mountains, rare. 
Also in Maine (Herb. Oakes). Spores apiculate, irregularly muriform- 
multilocular, more or less fuscescent, ##mmm. Cortex very coarsely cellu- 
lose.—L. inflecum, Nyl., inhabiting South America from Venezuela! 
to Bolivia! was originally observed in Mexico, and approaches so near 
‘arcte accedit,’ Nyl. Syn.) to L. Burgessii, that one might prefer to char- 
acterize the fine northern lichen as extending southward, not without 
modification, into the tropics.——18. L. myochrowm (Ebrh., Scher.). 
Trunks, throughout the United States, except the Pacific coast, infertile. 
Rocky Mountains, fertile; and Arctic America (Herb. Hook.) Greenland 
(Vahl in Th. Fr. Lich. Arct.) Islands of Behring’s Straits (C. Wright). By 
uniting, as constituents of the same.section (Mallotium) L. Burgessii with 
the species now immediately before us, Acharius may be said to have brought 
together what are on several accounts the most remarkable members of 
the present genus, and to have precluded as well the later elevation of the 
section to generical rank: the lichen first named being at once associable 
with ZL. myochroum, and yet not dissociable from LZ. Tremelloides. It is 
impossible not to recognize the affinity of L. resupinans, Nyl. (Mandon 
Pl. Boliv. n. 1715):on the one hand to LZ. Menziesii of the same collec- 
tion, and so to L. myochroum; as on the other to L. inflexum, Nyl. (Man- 
don J. ¢. n. 1721) and so to L. Burgessti. + 
The difficulties found in the way of a satisfactory determination of L. 
myochroum (Ebrh. 1785) as occurring throughout the North American 
continent, led to an examination of all the material at hand, immediately 
illustrative of this species; and the results of this examination will now 
be set down, with only the preliminary remark, that as I have accepted 
Scherer’s view, so far as it extended, of the limitation of the species, I 
follow him also in adopting for it what is without doubt the oldest name. 
Nylander’s exhaustive characterization (Syn. p. 127) of L. saturninum 
1 In this view it will not be surprising if the South American Mallotia should 
illustrate each other. It is the extraordinary difference of L. resupinans, in other 
respects closely resembling L. Menziesii, that the apothecia are produced (so far 
as appears, only) on the under side of the thallus, and conditioned therefore by the 
nap which covers that side; and the Bolivian specimens of L. inflerum shew that 
in this noble, southern exhibition of an extreme northern type, the nap is not 
rarely visible on both surfaces, and that apothecia in their normal position may 
exhibit a similar conditioning by a so to say foreign element, as if they were 
below; there being in fact, so far, no difference in the sides. This extension of 
the cortical cells into fibrils, above, is observable also in other specimens of L. 
inflecum (Venezuela, Fendler) and is sometimes rather conspicuous in the North 
American L. myochroum, as it is not wholly wanting in the European. 
