THE DISTRIBUTION OF COMMUNITIES 357 



existing maps by photography and to make records on the enlarge- 

 ments. Even these must be diagrammatic. In any case, the bound- 

 aries of the community must be exact, and this requires exact 

 observation. 



The higher social units, such as aUiances and orders, are more 

 easily mapped, since they usually occupy large, continuous areas. 

 They are best shown by strongly contrasting flat tones. It is difficult 

 to bring out the distribution of the larger units of vegetation by means 

 of cross hatching. This has been admirably done by Luquet (1926) in 

 his vegetation map of the Mont Dore massive (1:80,000). An inter- 

 nationally accepted color scheme would be very desirable. 



Communities with zonal distribution are easily and satisfactorily 

 shown by sketch maps with boundaries and shading in black and white 

 (Figs. 105, 161, 176). 



If there is interdigitation or mosaic arrangement of communities, 

 whole association complexes (the regularly recurring, intermingling 

 groups of associations) may be shown in one color or in one style of 

 cross hatching.^ 



Observations of vegetation and photographs from airplane are 

 not to be ignored as a means of geobotanic cartography. Stamp (1925) 

 has used this method successfully in the delta of the Irrawaddy. 



Line Transects.— Following the example of foresters, the approxi- 

 mate proportion of area occupied by plant communities of a uniform 

 region may be obtained by line transects. Parallel straight lines are 

 run through the area by means of compass and tape line, and the 

 length of these Hnes in each community recorded. The Finnish 

 foresters have determined the distribution of forest types in all Finland 

 by means of line transects 26 km. apart. 



Belt Transects.— For the study of gradual changes in vegetation, 

 as in profiles or the transition zone between two communities, the belt 

 transect is useful. This is a continuous series of quadrat areas running 

 across the profile or transition zone. In certain cases it is sufficient to 

 take one area in each well-defined zone of vegetation along the transect. 



iScharfetter (1928) has discussed in detail methods of mapping vegetation, 

 giving a good bibUography; and Brockmann-Jerosch (1931) has proposed an 

 international color scheme. 



