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Origin and Nature of Lichens — Part 2

The reindeer in Lapland feed almost entirely upon this lichen, and in times when food has been scarce, even man has been glad to avail himself of it.

In Sweden at one time the people made their bread from this lowly plant.

In moist places, velvety green ruffles (Peltigera, Colour Plate VII) spread on the ground or on stones and stumps, the edges of the ruffles set with fruit-disks curled in such a way as to resemble brown finger nails, or dogs' teeth. In the days when drugs were selected because of a fancied resemblance to the part of the body in need of cure, Peltigera canina was considered a cure for hydrophobia and received its specific name canina because of the resemblance of its fruit-disks to a dog's teeth. When dry the surface of the ruffles is a light quaker-drab, which quickly changes to a bright green when the lichen is damp.

It is on the bark of trees that one finds the richest harvest of lichens. They are found in the greatest profusion on the north sides of the trees and for this reason serve the wood-man as a guide through the forest. Emerson in "Wood Notes" refers to this, when he says:

"The moss upon the forest bark

Was pole-star when the night was dark."

(Colour Plate IX)

The encrusted lichens, Parmelia (Colour Plate V), and Sticta (Colour Plate VII) which grow flat on rocks and trees, cling so closely that they can with difficulty be separated. Their pretty gray or green mats dotted with shining brown fruits grow from the centre outward in an ever-widening circle, covering old fence rails, unpainted cabins, and all other hard unsightly things which Nature wishes to render soft and beautiful.

"O'er you low wall, . . . whose rough, discordant stone

Is massed to one soft gray by lichens fine

The tangled blackberry, crossed and recrossed, weaves

A prickly network of ensanguined leaves."

J. R. Lowell--An Indian Summer Reverie.

The ruby-throated hummingbirds know these lichens and so use them in decorating their nests (Plate I) as to make it difficult to distinguish them from lichen-covered knot holes. The Lungwort (Sticta pulmonaria, Colour Plate VII), so called from the resemblance of the pitted surface to the surface of a lung, does not encrust the bark on which it grows, but clings lightly to its support when moist and curls up its under white surface when dry, to protect its green surface. On the same tree with the Lungwort one often finds an hepatic (Porella platyphylla, Colour Plate XIV), with braided strands, and a moss (Neckera pennata, Colour Plate III) creeping around the tree trunk its strands in parallel rows.

On overhanging cliffs by lake or stream, or on huge rocks in the forest, one finds the oddest lichen of all, the Rock Tripe (Colour Plate XI). When wet, the velvety green shields lie flat, held by a stout cord at their centres. As the air around them becomes dry, the edges begin to curl, bringing the soot-black under surfaces to the light to form black tubes here and there over the rocks. With every change in the moisture of the air the Rock Tripe curls and uncurls, writhes, and twists; at one time presenting its gray or green surface, at another its black. This lichen is also used for food and is said to have saved the life of Sir John Franklin in the Arctic seas, when he was reduced to starvation.