VEGETATIOXAL ANALYSIS 69 



sparse and takes on a hibernal aspect very quickly. Where snow 

 patches remain well into the summer and provide a water supply 

 by melting gradually, the estival aspect may carry on for several 

 weeks after plants in less favorable sites near by have gone to seed. 

 Plants deeply buried under snow may not be exposed until so late 

 in the season that conditions are unfavorable for flowering, and, as 

 a result, they produce no fruit or seed. 



SYNTHETIC CHARACTERISTICS 



It has previously been pointed out that it is often desirable as 

 well as practical to consider a community in the abstract as well as 

 in the concrete sense. When a community is studied on this basis, 

 it becomes necessary to observe numerous stands and to determine 

 whether they actually do belong to the same community and to 

 what extent they vary from each other. It is desirable also to know 

 which species, singly or in combination, may be taken as indica- 

 tors, which species are only incidental, which ones are always 

 present, and which ones occur only when a stand develops under 

 a given set of conditions. 



Thus, for a complete synthetic analysis, it is desirable to have in- 

 formation on as many stands as possible, or at least enough stands 

 to be representative of the whole. These should be distributed 

 throughout the range of the community and under all the variety 

 of conditions in which they develop. Again, to make a proper an- 

 alysis, only those stands should be employed that are in a com- 

 parable stage of development or maturity and that are extensive 

 enough to include all the important species and most of the antici- 

 pated variations. 



Presence.— A most useful synthetic character involves merely 

 the degree of regularity with which a species occurs in the stands 

 observed. When the species present in each of the stands have 

 been tabulated, the presence of each is expressed by the percentage 

 of stands in which it occurred or by a five-degree scale of presence 

 classes. 



1.— rare (1-20% of the stands) 



2— seldom present (21-40%) 



3. -of ten present (41-60%) 



4— mostly present (61-80%) 



5— constantly present (81-100%) 



