3rd, Holding in reserve water storage. 
4th, Protection of lowlands from floods. 
5th, Provision of healthful resorts. 
4. Forest planting in unforested areas successfully attempted. 
(1) Afford shelter, firewood, building material. 
(2) Swamps reclaimed. Aided by eucalyptus. 
5. Enemies of the forest. 
(Un) elshitess 
(2) Carelessness of man. 
(2) --Climatic and soil factors! 
(4) Biotic factors. 
Ist, insects and animals feed upon leaves, 
buds, etc. 
2nd, parasites and wood destroying fungi. 
a. Some seed plants, rusts, mil- 
dews, molds, etc. 
b. Mushrooms most destructive. 
Gain entrance through bruises, 
broken branches, careless prun- 
ing, etc. 
6. Scavenger members of the forest societies. 
Mushrooms of incalculable use in the disposal of waste 
material and its conversion into food for the living 
theese 
XV. THE PRAIRIE AND PLAINS SOCIETIES 
1. Grassland Formations. 
Types of grassland. 
I. Savannas. Dry, warm, temperate, or  subtrepieal 
countries, yet sufficient moisture to permit number 
of trees. 
2. Prairie (meadows according to Schimper) cold tem- 
perate regions. Trees absent. 
3. Plains or Steppes, formation more open. 
Extent of prairie and plains in the United States. 
Prairie——100th meridian east to forests of Ilinois, and 
Indiana, including most of Dakotas, Nebraska, lowa, 
Southern Minnesota, Wisconsin, and large part of Kan- 
sas, Indian Territory, and extends north into Western 
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