FIELD WORK ON ECOLOGY 35 
(d) Having determined the dominant species, the subordinate. 
forms should be noted, as well as any signs of a struggle going 
on between the subordinate and dominant species, and the 
relation of plants to each other. In a beech-wood saprophytic 
plants will probably be found. To carry out this part of the 
investigation, a certain knowledge of botany is necessary, but 
even beginners in the subject can notice certain facts which 
are indications of the dependence of one plant on another. 
When a plant is not green, but colourless, it is probable that 
it is either parasitic or saprophytic ; then it should be ascer- 
tained on what plant it is growing, or on what substance it is 
feeding. After some experience observers get to notice that 
certain plants are commonly found together, and thus after a 
time, from the facts observed, it is possible to generalize. 
(e) The physical features of the district and of each area 
mapped out should be recorded in the note-book : 
(i.) Character of soil. A good geological guide of the 
district should be consulted ; the most accurate information 
about a district is generally found in the Z'ransactions of 
Local Scientific Societies. 
(ii) Slope of the district. 
_ (ii.) Water-supply, by river, lake, etc. ; rainfall. 
(iv.) Prevailing wind. 
(v.) Purity of atmosphere; freedom from smoke, ete. 
(f) To ascertain which plants are peculiar to the district in 
question, the list of plants obtained in a given district should 
be compared with those obtained in other districts, and a fresh 
list made of those which do not occur in other districts. The 
new list may be very small indeed ; it will depend on what 
“districts are compared with each other. Thus if a moor in 
the South of England is being compared with a moor in 
Scotland, where the latitude and altitude may be very 
_ different, there will probably be considerable difference in the 
floras. Or, again, if the vegetation of the seashore is being 
compared with that of an inland district, there will be far 
greater differences than if two inland districts are being com- 
pared with each other, 
