' 94 Lichens. 



LICHENS. 



Everyone is familiar with that tribe of flowerless plants, call d 

 Lichens, which spread like dry, hard, scaly crusts, over walls oil 

 trees, and rocks, but perhaps few think of the important part 

 which they perform in the vegetable world. To them ma 

 be well applied the title of Vernaculi, or bond-slaves, whi I 

 Linnaeus fancifully gave to the sea-weeds ; for they seem as it 

 were chained to the spot which they labor to improve for th 

 benefit of others. The way in which they prepare the sterile 

 rock on which they grow, for the reception of plants of higher 

 rank than themselves, is most remarkable. They may b 

 said to dig their own graves. While alive, they form a consid- 

 erable quantity of oxalic acid, which by its chemical action 

 eats a small hollow in the rock, in which the particles of th ' 

 lichen remain after its death. The moisture which is caught 

 in these cavities, finds its way into the cracks and crevices of 

 the rock, and when frozen, rends off minute fragments by its 

 expansion, and thus adds more and more to the forming soil. 

 Slowly and unwearily do successive generations of these bond- 

 slaves perform their duties, until at length there is soil enough 

 made for the growth of mosses, ferns, and other cryptogamia, 

 and at length, the barren and insulated rock, or the pumice 

 and lava of the volcano, are covered with sufficient depth of 

 mould for the nourishment of the luxuriant grass and the lofty 

 forest tree. Thus by the labors of these poor and insignificant 

 plants, are men enabled to reap their harvest, to feed their 

 cattle, to supply themselves with timber, on what was once but 

 a naked and desolate rock. One of the sternest and most 

 faithful delineators of Nature, Crabbe, has described such a 

 process, as it occurs on ruined buildings. We may be allowed 

 the hypercritical remark, however, that the terms seed, foliage, 

 and flower, are not strictly applicable to the Lichens, which 

 possess none of these. 



