In British Columbia, where the Cascade Range lies at no great distance from the Rocky Mountains, the western coniferous forest practically clothes the whole area from the coast to the main range, but further south, where the Cascade Range and its continuation the Sierra Nevada are widely separated from the main range, a dry and semi-desert region occurs, between the two, which bears a desert type of vegetation, including especially a plant related to our wormwood, called sagebrush, with cactuses in the warmer parts. Another area which is too arid to carry trees, except where local conditions raise the rainfall, extends from Texas northwards to about the latitude of Edmonton or Battleford, and lies in the "rain shadow" of the Rocky Mountains. This is the region of the Great Plains, mostly too arid to carry anything but herds of cattle, and mostly forming natural pasture, being thus analogous to the steppes of Asia. Eastward the rainfall increases, and we pass from the area of unreclaimed pasture to the prairies, now largely laid down to wheat and other food plants. Southward the Great Plains pass into the deserts of Mexico, but northwards they are separated from the northern coniferous forest by a belt of aspen, and it is in this region that the Canadians are steadily pushing the cultivation of wheat into the plains, wherever the local rainfall makes this possible. So far we have left south-eastern Canada and the whole of the eastern and south-eastern States out of consideration. Speaking very broadly, we may say that all this area is clothed by a forest of mixed coniferous and broad-leaved trees which is comparable to the forest which covers the greater part of temperate Europe. But it is not to be expected that a forest which extends from the northern shores of the Gulf of St. Lawrence to the extremity of the peninsula of Florida, that is, through about 25 degrees of latitude, should be uniform throughout. In point of fact, botanists distinguish three separate zones. In south-eastern Canada and the New England states the Weymouth pine (_Pinus strobus_) predominates, being accompanied by limes, ashes, maples, oaks, elms, chestnuts, and so forth. Further south, and especially further west, extending to the Mississippi plains, there is a deciduous forest extraordinarily rich in species. Practically all our common genera of forest trees are represented, sometimes by very fine species, but in addition there are many genera with no European representatives. Very striking is the abundance of magnolias (whence the name of magnolia forest sometimes given to this type), and species of the laurel family, as well as of liquidambar. The magnolias and liquidambar are especially interesting, because they once occurred in Europe, their disappearance there being probably caused by the glacial period as explained on p. 78.