732 
MAPPING AS AN ECOLOGICAL INSTRUMENT. 
decimetre strips. All the laths are marked with centimetre 
divisions, and the charting closely resembles that of a grid, 
except that even greater accuracy in measuring and mapping 
is essential. 
An excellent example of the use of the quadrat was 
provided by a small depression on the Erquy Bouche, which 
was filled originally with a dense growth of Salicornia europcea, 
chiefly of a peculiar apple-green type, and which was sur- 
rounded by hummocks colonised chiefly by Suceda maritima. 
The quadrat was four times the usual size, being one metre 
square, and was charted on a scale of 1/5 for a period of four 
years. The variation in the yearly colonisation of the area is 
well shown by the completed charts. 
An analysis was made of the number of each of the different 
species occurring in each year, and the changes are shown even 
more clearly by the figures than by the maps themselves. For 
instance, in 1905 there were 127 plants of the crimson type of 
Salicornia europcea, whereas in 1907, 1,498 were present ; in 
1905, 1,718 plants of Salicornia of all types were present, but 
in 1907 this number increased to 5,470. Such an analysis is 
only possible after the plants have been accurately charted — it 
would be a most difficult matter to carry it out on the area it- 
self, especially in patches where the colonisation is very dense. 
A further use can be made of the quadrant charts to show 
the distribution of individual species. From the maps of the 
Erquy hollow and hummocks several tracings have been made, 
each tracing bearing one single species. Those for 1905 show 
very clearly the way in which the apple-green Salicornia is 
segregated in the hollow in the middle of the area, whereas the 
intermediate and crimson forms of the same species shunned 
the hollow and colonised the higher ground of the surrounding 
hummocks. Also, both the green and purple types of Suceda 
maritima practically confined themselves to the hummocks. 
In 1907 all three types of Salicornia tended to congregate in 
the depression, comparatively few occurring on the higher 
slopes. The Suceda was fairly evenly distributed over both 
