300 THE FORMATION 
is unnecessary that they be repeated. Similarly, the questions which pertain 
to structure and development and to the surrounding Veg canon: are con- 
sidered in detail in the pages which precede. ‘ 
Fig. 80. Eritrichiare (Eritrichium aretioides), a community of the 
alpine meadow formation. 
CLASSIFICATION AND RELATIONSHIP 
350. Bases. Formations may be grouped with reference to habitat or 
kind, development or position. Classification upon the basis of habitat 
places together formations which are similar in physiognomy and structure. 
Developmental classification is based upon the fact that the stages of a par- 
ticular succession are organically connected or related, though they are nor- 
mally different in both physiognomy and structure. Grouping with respect 
to position is made solely upon occurrence in the same division of vegeta- 
tion. The formations thus brought together usually possess neither similar- 
ity of kind or structure, nor do they have any necessary developmental con- 
nection. Habitat and developmental classification are of fundamental value; 
regional arrangement is more superficial in character. All serve, however, 
to emphasize different relations, and, while the developmental system ex- 
presses the. most, they should all be used to exhibit the vegetation of a region, 
province, or zone. oo 
