LICHENS, 19 



ductions are entirely hidden from human 

 sight, and they afford a proof that organic 

 life is universally distributed. Our com- 

 mon sea-weeds do not grow at great depths ; 

 they abound along the coast, where they 

 cling to rocks, to shells, and to each other. 

 In warm temperate and tropical countries 

 the red species are numerous and very beau- 

 tiful. The waters of the Great Lakes are 

 remarkable for their entire lack of visible 

 algae. Many sea-weeds are edible, the most 

 widely known being the Irish moss. 



The LiCHEXS include a great variety of 

 peculiar plants which 

 are in many respects 

 like fungi. They dif- 

 fer from the fungi in 

 not being saprophytic 

 or parasitic, and in 

 growing much slower 

 and endurino' lono^er. 



Every one knows the dry, gray " moss " on 

 stones, logs, and the trunks of trees. (Fig. 

 21.) Nearly all lichens draw their nourish- 

 ment from the air and rain, although a few 

 live in water. In the interior of the gray 

 mass of the lichen are green or yellowish 

 granules, which possess the power of assimi- 



