The English flora - SeaweedAfrica

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192 LICHENES. [Psora.
powdery with a very thick rounded entire mealy border. Ach.
Syn.p. 170. Lichen Turneri, E. Bot. t. 857.
Trunks of old oaks and other trees.—Too near perhaps to L.
tartarea.
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31. L. citrina, Ach. (lemon-coloured Wall Lecanora); crust
leprous powdery indeterminate bright lemon-coloured, apothecia
scattered sessile minute orange-coloured with a pale yellow
powdery border. Sm.—Ach. Syn. p. 176. Lichen citriuus,
Ach. Prodr.—E. Bot. t. 1793.
On brick and flint walls in Norfolk. On wood, Yorkshire.
32. L. vitellina, Ach. (yolk of Egg Lecanora); crust leprous
granulated indeterminate bright greenish-yellow, apothecia
clustered sessile flat tawny- yellow at length convex and
brownish the border elevated crenate. Sm.— Ach. Syn.
p. 174. Lichen vitellines, Ehrh.—E. Bot. t. 1792.
Common on garden-pales, rails, deal boards, &c.
II. Thallus subfoliaceous, consisting of scales attached to the substance
on which they grow and more or less combined. Apothe-
cia always bordered and discoid, sessile (patellula).
Fam. VIII. Squamarie^e.
15. Psora. Hoffm. Psora.
Thallus defined, thick, formed of distinct, flattish or convex
tubercles or scales. Apothecia (patellulce) bordered, plane, at
length convex, placed at the sides of the scales, the border of the
same colour and substance as the disk Name ; -v^w^, a scurf.
1. P. c&ruleo-nigricans, (black and blue Psora); thallus of ir-
regular imbricated tumid powdery greyish warts or scales, apo-
thecia black irregular flattish from the margin of the scales at
length hemispherical. Lichen caruleo-nigricans, Lightf—E.
Bot. t. 1139. Lecidea vesicularis, Ach. Syn. p. 51. Psora vesi-
cularis and paradoxa, Hoffm.
Upon the ground and among rocks.
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2. P. atro-rufa, (red-brown Psora); thallus subcontinuous
lobed, the lobes angular smooth imbricated grey-brown, apothecia
sessile dark red-brown with a narrow border at length
confluent. Lecidea atro-rufa, Ach. Syn.p. 51. Lichen atro-rufus,
Dicks. Cr. Fasc. A. p. 2. t. 12./ 4. E. Bot. t. 1102.
On sandy ground, among Mosses, chiefly in the north of England.
3. P. scaldris, (olive and black imbricated Psora); thallus imbricated
often scattered in kidney-shaped lobes or scales ascending
distinct pale-olive powdery at the edge and black, apothecia flat
irregular black-bordered. Sm.—Lecidea scalaris, Ach. Syn.
p. 52. Lichen scalaris, Ach. Prodr E. Bot. t.
cnphmts, Dicks.—Psora ostreata, Hoffm.
1501. L. leu