THE CONTEXTS OF THE SOIL 



33 



unttintr liino ami sulfurio iiciil, sulfate of liiue or pypsuni is pro- 

 duofil, is cheiuical action. 



31(1. KnowUiljje of thi« work of tho t'arthworra in buildinp 

 soils dates practically from the issue of Darwin's remarkable 

 book, "The Formation of Vegetable Mould, through the Action of 

 Worms," which the reader should consult for particulars. The 

 subject is also considered briefly in King's "Soil," Chap, i., which 

 also discusses the general means of soil -building. 



3'Ji. As an example of the formation of organic soils in the 

 tropics, read accounts of the mangrove. Its mode of propagation 



I 



•'l^'..^ 



t'lK. -t. A uella lu nu unliunl. 



is explained, with illustrations, in Bailey's '" I.K?ssonM with Plants," 

 pp. n71-:»74: the tree is also d««scribed in Chap. v. of Gaye's 

 ''Great World's Farm." As an example of a formation of a peat 

 bog by the growth of sphagnum, read Ganong "On Raised Peot- 

 bogs in New Brunswick," Botanical Gazette, pp. I2:J-l"-'n. May, 

 1801 Sphagnum is moss which grows in cold bogs. Nurserj'iueo 

 mod florists use it in tho packing of plants. 



