948 XII. LICHENES. 



primarii, constitutivi, reproductorii, liberi, firi, difflttentes, jiersisteiitcs, emersi, semi-emersi, immersi, indusim, 

 ntffultorii, sporophori, &c. I spare you the rest: all this implies that it is but a cell infinitely varied. . . .' 



Lichens are found in all climates, but their numbers increase as we recede from the equator; 

 they usually grow, as we have said, on earth, stones, leaves, bark, and other Lichens ; also on Mosses, 

 dead wood, bones, leather, old iron, the old windows of country churches, which they decompose in 

 process of time, under the influence of dnmp, by extracting a little potash ; such is especially the case 

 with I'annelia parit-tina, which grows on almost anything. Some prefer calcareous rocks, others 

 granitic ; some inhabit rocks moistened by the sea (Liehina, Roccella). The edible Lichen (Lecanora 

 escttlenta) is quoted in M. Le"veille"s letter in support of the opinion that Lichens derive their nourishment 

 from the atmosphere. The thallus of this species occurs in little rounded masses the size of a filbert: the 

 interior is white and crustaceous ; the surface is grey, uneven, wrinkled, with warts enlarged into lobes ; 

 these lobes overlap irregularly, but have evidently been developed centrifugally, and in consequence of 

 the early interlacing of their ramifications, or rather of their destruction, have formed a body solid 

 within, and imperfectly foliaceous without. This Lichen, which has been found in Algeria, is frequently 

 met with in the most arid mountains of the deserts of Tartary, where the soil is chalk and gypsum, and it 

 grows on the soil amongst the flints, from which it is only to be distinguished by practised eyes. Large 

 quantities are found in the Kirghis deserts, to the south of the river Jafk, at the foot of gypsum hills 

 which surround the salt lakes. The traveller Parrot brought home specimens of this Lichen, which, at 

 the beginning of 1828, had fallen like rain in several parts of Persia. He was assured that the ground 

 was covered with it to a height of eight inches, that cattle eagerly ate it, and that the natives 

 gathered it as a manna fallen from heaven, and made bread of it. The naturalists Pallas and 

 Professor Eversmann, who observed it growing, never found a single specimen attached to any object; 

 they gathered some of the size of a pin's head; all were absolutely free of support. Eversmann con- 

 jectured that this Lichen had originally germinated around a grain of sand, which it had then entirely 

 surrounded ; but observation not having confirmed this hypothesis, he has been led to admit that the 

 germ of this Lichen develops in all directions, and derives its nourishment from the surrounding air. 



Lichens, which mostly contain starch, may, like Lecanora esctilenta, contribute more or less to 

 the food of men or animals; such is the Reindeer Lichen (Cenomyce rangiferina) , which serves as 

 pasturnge, in the northern regions, to the herds of reindeer and some other herbivorous mammalia. 

 The Iceland Moss (Cetraria islandica) and the ' Pulmonaire de Clieno ' (Sticta pidmonacca) contain 

 a bitter and mucilaginous principle, which cause them to be used medicinally in diseases of the lung.s. 

 Variolaria awiara and several Parmelitte are used in certain countries as febrifuges and nnthelminthics. 

 Peltiyera canitia formerly entered into the composition of a remedy for hydrophobia. Some Lichens also 

 yield useful dyes ; as Jtoccella, Lecunora tartarea and Purella, and Purmclia s(t.ratilix, which yield the 

 Orchil and Cudbear of commerce. 



Lichens also play an important part in the economy of nature. It may be said that they, with 

 Mosses, have been the first cultivators of the soil; or rather, that is they who have created the soil that 

 covers the great mineral masses of the globe. It is of their detritus that are formed even now on the 

 most arid rocks the first layers of humus, or earth, in which plants of a higher order speedily take root, 

 and their dtSbris, accumulating during centuries, finally form a soil capable of sustaining and affording 

 nourishment to the largest vegetables. It is generally thought that Lichens, as well as Mosses, are 

 injurious to the trees on which they grow : this opinion does not rest on any solid foundation. 1 



We find in a memoir recently published by Dr. Lortet some very interesting details regarding the 

 action of electricity on the spermatia of Lichens and Fungi. Neither static nor voltaic electricity exercises 

 any influence on these organs, but electricity developed by the induction coil presents a most curious 

 phenomenon. The spermatia, according to M. Lortet, who adopts in this the opinion of M. Itzigsohn, 

 are endowed with very active movements ; contrary to the ideas of most botanists, who look upon these 

 movements as a Brownian oscillation, M. Lortet perceives no difference between these movements and 

 those of antherozoids, although the strongest magnifying powers have not enabled him to detect nny 

 vibrating hairs on the spermatia. However this may be, these bodies, placed in water, execute two 

 extremely quick movements the one of oscillation, which consists of a tremulous motion of the organ 



' Lichens and Mosses are not parasitic; but when veloping young shoots, and interfere with the develop- 

 they clothe trees they impede the circulation of air, and ment of cambium and the evolution of the foliage, 

 hasten decay. They further intercept light when en- ED. 



