94 THE WORLD OF LIFE 



work such as the present. We will now proceed to a 

 brief consideration of the nature and meaning of the facts 

 set forth in the preceding chapters. 



The evidence, collected with extreme care for many years 

 by Mr. Woodruffe-Peacock (as explained in Chapter II.), has 

 shown us how curiously the number of species differs even 

 on the smallest adjacent areas. In the same field, even 

 when apparently alike everywhere in soil, in aspect, and 

 in contour of surface, every plot of 16 feet square has its 

 individuality. It will differ from each of the eight adjacent 

 plots either in the number of the species it contains, or in 

 the species themselves, or in the proportions of the individuals 

 of the various species. They are thus seen to be affected 

 by very small differences, such as moisture, or aridity ; more 

 or less shade from hedges, trees, or woods ; shelter from 

 or exposure to winds ; by the vicinity of pits or quarries, 

 woods, ponds, or streams. 



Now this one fact of response to the minutest change 

 of conditions in the arrangement of a few species over almost 

 identical adjacent areas is as much a case of adaptation 

 to the environment through the mutual interaction of the 

 various species — a struggle for existence on the very 

 smallest scale — as any of those larger and more complex 

 cases which Darwin first made known to us. 



Coming now to the fields themselves of various shapes 

 and dimensions, and each limited by definite boundaries 

 of hedge and ditch, bank or wall, spinneys, plantation or 

 woods, we have, in our country especially, a series of unit- 

 areas which may be said to form the first step in the study 

 of botanical geography, and which leads us on through 

 successively larger areas to regions and continents. 



In regard to these fields, the v/riter above quoted not 

 only states their precise differences in the numbers of their 

 species and the presence of certain species and absence of 

 others which give to each its individuality, but he is able 

 in many cases to define the causes of that individuality. 

 Besides the ordinary variations of soil, we have to take 

 account of the effects of diversity of treatment as meadows, 

 pasture, or fallow land, each resulting in a characteristic 

 grouping of species easily recognisable over wide areas. 



