Ch. XIV] THE FORMATIONS 585 



suitable undergrowth and ground plants. A Dwarf Forest, 

 composed mostly of dwarfed evergreen trees (" Elfin Trees"), 

 merging down to creeping Willows, etc., gives the transition 

 from true forest to open plains beyond the tree line in high 

 northern regions and on mountains, where it forms often 

 almost impenetrable growths ("pucker brush," "Krumm- 

 holz," etc.). 



The Shrub Formations. These are found where condi- 

 tions forbid trees, as locally in exposed places in different parts 

 of the world ; and often they bear appropriate local names, 

 e.g. garigue and maqui in Europe, thickets in England, chap- 

 arral in western America, though this form approaches a 

 desert formation. 



The Grassland Formations. These occur where the 

 climate would permit trees and shrubs, but local conditions 

 prohibit them. They are composed of Grasses and Sedges, 

 with associated plants of conformable habit. Such are our 

 own Meadows, where we artificially prevent growth of 

 trees. The Prairies are Grass Formations from which 

 trees and shrubs have long been excluded, perhaps by the 

 periodical fires. In mountainous districts often occur open 

 grassy Parks, while everybody has heard of the Alpine 

 Meadows found above the tree lines on mountains, and 

 composed of a turf of low-growing perennial herbs having 

 very beautiful flowers. 



The Plains form a transition from grass lands to 

 deserts, as illustrated in our own western plains, with 

 scattered bunch grasses. The Steppes of Asia are allied, 

 as are the Savannahs of Africa, and the Pampas of South 

 America. 



The Desert Formations. These are "open" formations, 

 with spaces of bare soil between the plants, which include the 

 extreme xerophytes of North America. The Desert Forma- 

 tion has associations of succulent Cacti, and of Sage Brush. 

 The deserts of Asia, Africa, and Australia have, of course, 

 their own associations. 



