that they look as if they had been smoked, or rubbed over with gunpowder.

59. ARTHONIA.

1. A. astroidea, crust thin, even, white or greyish-white; apothecia black, numerous, even with the crust, rounded, more or less stellate.-Hook. Scot. ii. 36.

Hab. On the bark of the ash and elm, occasionally.

2. A. swartziana, crust thin, even, greyish-white; apothecia black, even with the crust, numerous, short, somewhat linear, irregularly branched.-ACH. Syn. Lich. 5.

Hab. On the ash, near the Retreat, Berwickshire.

When I mention that the names to my specimens were attached by Mr ARNOTT, I need scarcely add that no doubt can be entertained of the correctness of their application. I have described them without reference to the descriptions of others, and to me the species appear too nearly related.

60. SPILOMA.

1. S. tumidulum, crust very thin, even, greyish-brown; apothecia tile-red, irregularly oblong, crowded, rough or granular.Hook. Scot. ii. 35.

Hab. On the bark of trees. On the hazel in the dean at the Pease-bridge.

61. VARIOLARIA.

1. V. amara, crust rugose, cracked, uneven, subpulverulent, white or greyish; warts of the apothecia appressed, plano-concave, margined, bearing soridia of the same colour as the crust. Hook. Scot. ii. 46. Lichen fagineus, LIGHTF. Scot. 807. WITH. iv. 4.

Hab. On the bark of the ash, birch, and oak, not uncom

mon.

The crust of this lichen is intensely bitter, and it imparts this bitterness readily both to water and alcohol. BRA

CONNOT found in the 100 parts, 18 parts of lime, combined with 29.4 of oxalic acid. Nearly the same quantity of oxalate of lime was found in Porina pertusa, Isidium corallinum, Lecanora tartarea, and some others which do not occur in this neighbourhood. "The oxalate of lime bears the same relation to the Cryptogamia as carbonate of lime to corals, and phosphate of lime to the bony structure of the more perfect animals. The oxalate of lime diminishes gradually in the family of lichens, in proportion as the species lose their granular crustaceous texture, and approach more and more to the membranous or cartilaginous, although these latter also contain a considerable quantity of this salt. From the vast abundance of these lichens, it is evident that they may afford a means of obtaining oxalic acid in great quantity, and at a cheap rate."-Edin. Phil. Journ. xiii. 194.

62. VERRUCARIA.

1. V. epigea, crust yellowish-green, thin, granular when dry; apothecia small, tubercle-like, dull black, with a central lighter coloured nucleus.-ACHAR. Synop. 96. Lichen terrestris, Eng. Bot. t. 1681.

Hab. Dry barren banks, near Berwick, rare.

ACHARIUS says the tubercles are black internally, but in our specimen the nucleus is rather buff coloured. When wet, the crust is soft and somewhat slimy.

2. V. epidermidis, "crust exceedingly thin, spreading, quite white; fructification minute, roundish, sub-elliptical, tubercles semi-immersed, the interior white."-GREV. Fl. Edin. 353.

Hab. On the bark of the birch, rather rare.

63. PORINA.

1. P. pertusa, crust bluish-grey, even, thin, spreading, tubercular or warted, the warts perforated or marked with depressed black points, internally cellular, whitish.-Hook. Scot. ii. 45. Lichen pertusus, LIGHTF. Scot. 802. WITH. iv. 16. Sphæria pertusa, BOLT. Fung. t. 126. DILL. Musc. t. xviii. f. 9.

Hab. Trunks of trees, most common on ash.

The Porina leioplaca of ACHARIUS (MOUG. and NEST., No. 847.) is surely nothing but P. pertusa in an early state, but if it is to be considered a distinct and perfect species, it must be added to the British list of lichens, for I have gathered it in Berwickshire on the birch, and it is probably far from uncommon.

64. ENDOCARPON.

1. E. Weberi, frond depressed, thick and somewhat leathery, foliaceous, lobed; lobes crowded, the interior irregularly convolute, raised, the exterior undulate with rounded sinuate margins; upper surface greenish-grey, smooth, beneath fawn coloured and smooth; orifices punctiform, black, slightly raised.-Hook. Scot. ii. 45. GREV. Fl. Edin. 329. DILL. Musc. t. 30, f. 127.

Hab. On rocks by the sides of rivulets. On the linn in Humbledon Dean above Wooler, abundant, W. C. Trevelyan, Esq.

On drying, the colour of the upper surface becomes a greyishpink.

65. LEPRARÍA.

1. L. flava, crust spreading, equal, thin, somewhat cracked, bright yellow, composed of sub-globose granules.-Hook. Scot. ii. 73. Eng. Bot. t. 1350. Lichen flavus, WITH. iv. 3. Byssus candelaris, LIGHTF. Scot. 1005.

66

Hab. On timber long exposed to the weather; and, with LIGHTFOOT, we have sometimes seen it cover old mosses, which appear exactly as if they had been powdered with flour of brimstone."

2. L. latebraram, grey, pulverulent, undefined, thick; granules mixed with fibres. Hook. Scot. ii. 73. Eng. Bot. t. 2147. (too green.)

Hab. On rocks in caverns, and on stumps of hawthorn at the roots of old hedges, common.

In caverns and in crevices this ambiguous thing" forms light convex soft cushions, easily separable from the rock, their central part being elevated by age, and in a manner vaulted underneath." It is thinner when growing on trees, the

base of which, in shaded situations, it often covers with a light grey pulverulent coat; and in this latter situation I have found, lying on the crust, small spherical bodies of a shining red colour, which are a species of Sphæria.

3. L. alba, pure white, uniform, pulverulent. Eng. Bot. t. 1349. Lichen albus, WITH. iv. 1. Byssus lactea, LIGHTF. Scot. 1007. Lecidea alba, Hook. Scot. ii. 38.

Hab. On hypna and lichens in shaded situations, common, making them appear as if they had been white-washed. The Lepraria have but slight claims to be considered perfect plants. They appear to be true lichens struggling for existence in places unsuited to their full development, and altered in appearance by their situation.

Besides those partial uses which have been mentioned under particular species, lichens play a most important part in the establishment of vegetation at the surface of the globe. "When we remark the hardness, the dryness, and the bareness of rocks, we should scarcely imagine that their summit might one day be crowned with forests; and yet this great work is carried on under our eyes, and even in the midst of our habitations. We observe the walls covered with greenish spots, which grow from humidity, and which the light and heat reduce to black and tenacious spots; these are so many byssi which have essayed to establish vegetation there, as well as upon the most polished statues and marbles; it is they which impress the seal of age upon our old castles and gothic edifices. Elsewhere, particularly upon rough stones, we see spreading out into broad plats those lichens of various colours, like the ulcerous crusts which corrode the skin of animals; they scoop out and corrode the surface of rocks, and deposit in the va cuities which they have formed, the portion of earth produced by their destruction. Although in very small quantity, this earth suffices to administer to the development of lichens of a higher order. Their debris, added to those of the former, furnish a small layer of earth sufficient for the existence of mosses of an inferior order, to which, in like manner, succeed more vigorous species." Edin. Phil. Journ. xvi, 66. See also the Quart. Review, vol. xxxviii. p. 438.

"Seeds, to our eye invisible, will find

On the rude rock the bed that fits their kind;
There, in the rugged soil, they safely dwell,
Till showers and snows the subtle atoms swell,
And spread th' enduring foliage;-then we trace
The freckled flower upon the flinty base;
These all increase, till in unnoticed years
The stony tower as grey with age appears.
With coats of vegetation, thinly spread,
Coat above coat, the living on the dead:
These then dissolve to dust, and make a way
For bolder foliage, nursed by their decay:
The long-enduring Ferns in time will all
Die and depose their dust upon the wall;

Where the wing'd seed may rest, till many a flower
Shew Flora's triumph o'er the falling tower."

CRABBE