GROWTH OF GEOLOGY. 267 



relation to the earth has been more and more 

 thoroughly appreciated. 



" The sea-weeds cling around the shore and lessen 

 the shock of the breakers. The lichens eat slowly into 

 the stones, sending their fine threads beneath the sur- 

 face as thickly sometimes * as grass-roots in a meadow- 

 land/ so that the skin of the rock is gradually weath- 

 ered away. On the moor the mosses form huge sponges, 

 which mitigate floods and keep the streams flowing in 

 days of drought. Many little plants smooth away the 

 wrinkles on the earth's face, and adorn her with jewels ; 

 others have caught and stored the sunshine, hidden its 

 power in strange guise in the earth, and our hearths 

 with their smouldering peat or glowing coal are warmed 

 by the sunlight of ancient summers. The grass which 

 began to grow in comparatively modern (i. e.. Tertiary) 

 times has made the earth a fit home for flocks and herds, 

 and protects it like a garment; the forests affect the 

 rainfall and temper the climate besides sheltering mul- 

 titudes of living things, to some of whom every blow of 

 the axe is a death-knell. Indeed, no plant from Bacte- 

 rium to oak-tree either lives or dies to itself, or is with- 

 out its influence on earth and beast and man." * 



From the vegetable drift borne down often in 

 immense quantity by rivers to the diatom ooze which 

 accumulates in some parts of the deep-sea, there are 

 many modern examples of additions made to the 

 earth by plants; from the protective action of sand- 

 binding grasses and sedges, or of mangrove belts 

 along the coasts, to the action of many Algae in 

 forming deposits of carbonate of lime, there are many 

 illustrations of processes at present going on in 

 which plants play a part of much geological in- 

 terest. 



* J. Arthur Thomson. The Study of Animal Life, fourth 

 edition, London, 1901, p. 25. 



