522 RELATION TO ENVIRONMENT. 



arid regions by irrigation in addition to cultivation. In a broad 

 sense there are two general types of the culture formations: 

 ist, the vegetation of cultivated fields; 2d, the vegetation of 

 waste places. There is not space in this book even for a satis- 

 factory outline, and no discussion of these formations will be 

 given. Only a few of the prominent culture formations will 

 be mentioned at this place. 



995. Vegetation of cultivated fields. Here belong the field 

 and garden crops. Examples: the cereals (wheat, etc.), corn, rice, 

 potatoes, meadow grasses, pastures, cotton, cane, beans, beets, 

 orchard fruits, berries, vegetables, gardens of various kinds, 

 and forests in some cases. 



995a. Vegetation of waste places. This would include ground 

 once cultivated or cleaned and later abandoned for the time or 

 devoted to other purposes. Examples: the vegetation of road- 

 sides and road embankments, of abandoned fields, of yards or 

 areas not devoted for the time to agricultural or horticultural 

 purposes. The plants growing in such places are usually called 

 "weeds," though "weeds" are often very abundant in culture 

 formations and sometimes develop to such an extent as to en- 

 tirely overcome them. 



V. Principal and Individual Formations. 



996. The principal formations. The term formation, or 

 principal formation, is used by some in speaking of the dominant 

 vegetation of places more or less limited by distinct physiographic 

 areas. In this sense the formation, or principal formation, is 

 not very different, if at all, from a single edaphic formation, or 

 single water formation. It is made up of the different individual 

 formations which are the dominant vegetation forms in the 

 zones or plats which are usually present on different portions 

 of the same physiographic area. 



997. Plant societies. The term plant society is used by 

 some in a broad sense to include all those plants living together 

 over an area possessing a nearly or quite uniform ground con- 



