THE PLANT FORMATION 



233 



II, Mesophytic formations 



1. Shade plant formations 2. 

 (9) forest 



(10) grove 



(11) open woodland 



(12) thicket 



III. Xerophytic formations 



(17) desert 



(18) plains 



(19) prairie 



(20) sanddraw 



(21) strand 



Sun plant formations 



(13) meadow 



(14) pasture 



(15) cultivated field 



(16) wastes 



(22) dune 



(23) cliff 



(24) saline area 



(25) heath 



Fig. 92. -A bog of mar-sh-marigolds, a hydrophytic formation. 



247. Developmental or physiographic classification. All the 



formations that belong to one succession are classified together 

 by virtue of being stages in the development of it. Such a groujiing 

 is often connected with changes in physiograi)hy. The foi-ma- 

 tions are in each case arranged in the sequence found in the i)ar- 

 ticular succession. A developmental classification is of great 

 importance because it summarizes the history of striking changes 



