STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 109 



temperate zone peats of North America and Europe as well as about 

 those of the arctic and sub-arctic areas. In North America, the 

 passage from subtropical peats of Florida to those of the subarctic 

 areas is gradual ; the plant-life changes, but the peat varies little in 

 character. The fact is certain that in the tropics as in the tem- 

 perates, peat accumulates where the necessary conditions exist and 

 that it does not accumulate in either when those conditions are 

 wanting. 



4. Peat may be derived from any land plant, but ordinarily the 

 flora contains many types. The constituent plants vary at the several 

 horizons in a deposit, but for the most part the peat does not consist 

 of any one plant or class of plants. Occasionally a layer consists of 

 remains of a single species, but the occurrence is comparatively rare. 

 The peat-making forms are not the same at all localities. In northern 

 Europe, certain mosses, chiefly Sphagnum, are the important constitu- 

 ents in the upper layers, so also in some parts of North America ; but 

 there are considerable areas in both regions where mosses are either 

 wanting or are wholly unimportant. Sedges have been the efficient 

 peat-producers in much of the north temperate, even at some tropical 

 and subtropical localities. But there is no limitation ; conifers, palms, 

 deciduous trees, mosses, sedges, in a word, any water-loving plant or 

 any plant preferring a slightly acid soil will yield peat under similar 

 conditions ; the soft parts become a pulp but the harder parts change 

 more slowly. More than 100 years ago, Al. Brongniart called atten- 

 tion to peat in Holland composed of leaves of conifers and Reinsch, 

 almost 75 years ago, observed similar peat in Germany ; the forma- 

 tion of peat from ofifal of oaks and conifers is a familiar phenomenon 

 in the Rocky Mountain region. 



In Tierra del Fuego, where conditions are subarctic, the chief 

 peat producer, according to Darwin, is a sedgelike plant, Astelia 

 pumata; in the Falkland islands, every plant is a peat-maker while 

 at Chiloe, Astelia pumata and Donatia magellanica make up the mass 

 of the peat. The Nile Sudd consists chiefly of sedges and grasses; 

 in Florida, not only conifers of various types but also grasses and 

 sedges contribute, and even the hyacinth has become important. But 

 they all give peat; the sedge-conifer-moss peat of Germany is almost 



