214 YIEWS OF NATURE. 



Yet everywhere man rejoices in the presence of nourish- 

 ing plants. Even where from the depths of the sea, a volcano 

 bursting through the boiling flood, upheaves a scoriaceoufi 

 rock, (as once happened in the Greek Islands) ; or, to instance 

 a more gradual phenomenon, where the united labours of the 

 coral animal (Lithophytes) (7) have piled up their cellulai 

 dwellings, on the crests of submarine mountains, until after toil- 

 ing for thousands of years their edifice reaches the level of the 

 ocean, when its architects perish, and leave a coral island. 

 Thus are organic forces ever ready to animate with living 

 forms the naked rock. How seeds are so suddenly trans- 

 ported to these rocks, whether by birds, or by winds, or by 

 the waves of ocean, is a question that cannot be decided, 

 owing to the great distance of these islands from the coasts . But 

 no sooner has the air greeted the naked rock, than, in our 

 northern countries, it gradually acquires a covering of velvet- 

 like fibres, which appear to the eye to be coloured spots. 

 Some of these are bordered by single and others by double 

 rows, while others again are traversed by furrows and divided 

 into compartments. As they increase in age their colour 

 darkens. The bright glittering yellow becomes brown, and 

 gradually the bluish-grey mass of the LeprariaB changes to a 

 dusty black. As the outlines of this vegetable surface merge 

 into each other with increasing age, the dark ground acquires 

 a new covering of fresh circular spots of dazzling whiteness. 

 Thus one organic tissue rises, like strata, over the other; and 

 as the human race in its development must pass through 

 definite stages of civilization, so also is the gradual distri- 

 bution of plants dependent on definite physical laws. In 

 spots where lofty forest trees now rear their towering summits, 

 the sole covering of the barren rock was once the tender 

 lichen ; the long and immeasurable interval was filled up by 

 the growth of grasses, herbaceous plants, and shrubs. The 

 place occupied in northern regions by mosses and lichens is 

 supplied in the tropics by Portulacas, Gomphrenas, and othei 



