198 A. G. Tansley. 
yet in its infancy, and the pioneer work of Drude, Flahault and the 
Smiths has only begun to shew us its possibilities. The various 
difficulties that surround it cannot be entered upon here, but one 
point of importance may be mentioned. The vegetation of an area 
cannot be presented once for all on a single map. Different maps 
are required for bringing out different aspects of the flora, and maps 
on different scales are absolutely essential. A scale suitable for 
exhibiting the main features of the vegetation of a given region 
often requires supplementing by larger scale maps of portions of 
the region to shew more detail. Again a scale adequate to the 
display of the leading vegetation-features of one region may shew 
nothing worth shewing in another part of the country. 
For these reasons I should like to see a central committee 
formed for the systematic survey and mapping of the British Isles. 
The time necessarily taken by the travelling and field work makes 
it most desirable that such work should be planned on a compre¬ 
hensive scale and the proper co-ordination of the results obtained 
in different parts of the country makes co-operation, frequent 
consultation of different workers, and I think, in the case of the 
less experienced, some kind of central direction, of great importance. 
A further point which such a central committee might hope to deal 
with, and one which if dealt with successfully would do much to 
remove what I have always thought is one of the most crying 
examples of the waste of good work and sound knowledge in the 
field of modern botany, is the utilisation of the work of the local 
botanist and the local field club. Scattered up and down the 
country are scores of men whose hobby is botany and whose 
acquaintance with their local floras is absolutely unequalled. Too 
often they carry with them to their graves knowledge which would 
be of the greatest value in helping to build up a picture of the 
vegetation of the country as a whole. Convince them of the 
interest of ecological survey work, and you would secure their 
co-operation in working out and mapping local floras from that 
point of view, which with the requisite general knowledge of methods 
and a certain amount of help and direction, they would do a 
hundred times better than a visiting botanist, with no knowledge of 
the locality. The extensive co-operation and co-ordination of 
workers which might result in the course of a few years would 
probably lead to a very striking development of the whole subject. 
A real danger to which workers in this field are exposed could 
be largely avoided by properly organised work under a general 
scheme. The great variation in detail of plant-associations, which 
is a result of the very complex factors combining to produce the 
