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With it has often been confounded, and by Acharius as well, a state of 
the next.——In P. placorodia (Ach., Nyl.) the latter author has satisfac- 
torily united (Lich. Scand. p. 106) the North American lichen described 
as P. placorodia by Acharius (Tuckerm. evs. n. 71) with the European 
P. aleurites, v. diffusa, Ach. The first of these plants belongs evidently 
to the cetrarieform wing of Parmelia, and was described as Cetraria 
in Syn. Lich. N. Eng., being well comparable (except in the spermogones) 
with C. ciliaris, on rails, its constant companion, and C. awrescens. The 
other, more unmistakably Parmeliine, and always scurfy, so as to resem- 
ble a good deal P. Borreri, v. rudecta, is a common rail-lichen of New 
England, not rarely fertile, at least in the interior. The spores, as Koer- 
ber (Syst. p. 73) first pointed out, well distinguish this species from the 
immediately preceding. The two, together with P. ambigua, are remark- 
able (Nyl. 1. c.) for their elongated, cylindrical spermatia. P. Fendleri 
(Tuckerm. in Nyl. Ewin. Gén. Lich. Calif. p. 14. Platysma, Nyl. Syn. 1, 
p. 309) discovered on coniferous trees in New Mexico by Fendler, occurred 
to me abundantly on pines, and rails adjoining in Maryland, and has 
been found by Mr. Ravenel (also on pines) in South Carolina, and by Dr. 
Michener in New Jersey; the tree specimens being more lax and diffuse, 
and the rail-lichen with more of the habit of similar conditions of Cetra- 
ria ciliaris, with which it grows. The plant compares exactly in these 
respects with the original P. placorodia, Ach. (Tuckerm. ers.) and equally 
with that, belongs, as it appears to me, quite without doubt, to Parmelia. 
Spermogones never marginal in the strict sense in which this is true of 
Cetraria; nor in fact differing in any important respect from those of 
Parmelia stygia. —— P, olivacea, Ach., here as elsewhere is much modi- 
fied in its saxicoline states (v. proliza, Ach., Nyl.) becoming at length 
narrowly divided, and passing often into densely imbricated small lobes 
(f. panniformis), or besprinkled with rounded soredia (f. dendritica, Nyl. 
Imb. Sprengelii, Floerk., Koerb.) The last has only occurred to me (on 
granite rocks in the White Mountains, and near Boston) sterile, but the 
smooth form has been found fertile in Vermont (C. C. Frost). —— P. mol- 
liuscula, Ach., as interpreted by Nylander (P. chlorochroa, Tuckerm. 
Obs. Lich. 1. c. 4, p. 383) which represents, in the ochroleucous, that ever- 
nioid tendency which we have found in both the other series, is found 
here abundantly in the lower regions of the Rocky Mountains; as also at 
the Cape of Good Hope and in Peru (Nyl.) I also possess it from the 
Asiatic deserts of Soongaria (Herb. Spreng). —— What is P. congruens, 
Ach., Nyl.? The lichen was originally described from specimens collected 
by Swartz, and he says of it (Lich. Amer. p. 5) that it inhabits trees in 
North America, and, more particularly, in New England. P. congruens 
of Herb. Floerk. (Camtschatka, Tilesius) is possibly the same with 
P. molliuscula v. vagans, Nyl., now referred by him (Lich. Scand.) to a 
form of P. conspersa; and is, at any rate, a rock-lichen. P. congruens, 
Spreng. Syst. 4, 1, p. 286, is, to judge by his own specimen (Herb. Spreng 
