and hard fern, grasses such as spreading milium, tufted aira, and sedges such as pendula 

 sylvatica. These and many others should be searched for from the point of view of their 

 absence as well as their presence. This is an intensely stimulating exercise. Why should 

 we not find primrose, for example, when it is common in another wood less than a mile 

 distant. In my own neighbourhood, extensive woodland stretches from Chilham to 

 Eastwell. In the northern half three uncommon plants flourish : the green hellebore, 

 wild columbine and the lady orchid. In the southern half these are absent. Occasionally 

 a single plant of columbine or lady orchis is found but it never spreads and dies out in a 

 few seasons. I have introduced both into my own dell but they do not thrive and show 

 no signs of becoming naturalised. The reason eludes me. It is likely to be due to soil. 

 Negative observation gains results by provoking thought. 



The third principle provides reasons and enables us to check our results. We do not 

 concern ourselves with laboratory procedure but study the importance of human influence 

 upon environment. If a stretch of country is left undisturbed, it eventually attains a state 

 of stability which is termed its climax. Examples of climax vegetation are stretches of 

 moor, bog, shingle, sand dunes, the faces of cliffs, the summits of mountains, there survive 

 beautiful and precious native species of our flora and fauna. In the wilder parts of 

 Britain much of this type of country still survives as such, but our county of Kent owes 

 its diversity and much of its ecological interests to human activity. What climax vegeta- 

 tion remains consists in a very few patches of bog as at Hothfield, shingle as at Dungeness, 

 sand dunes as at Sandwich, beechwoods on the Downs, the chalk cliff's and saltmarshes. 

 It is amazingly restricted to coastal strips. Inland man largely controls the pattern. 

 The faces of the Downs are grazed, ploughed up and quarried. The woods are coppiced, 

 th^ water meadows are drained, ditches are cleared out yearly. However, although much 

 is lost, much also is gained. The verges of roads, railway banks and quarries provide 

 happy hunting grounds. If the Weald were left untouched its climax would be likely to 

 be impenetrable forest where little undergrowth could survive. These activities are, from 

 our point of view, fortuitous experiments of supreme importance. Seeds are scattered 

 along the roads in shingle brought from elsewhere. Aliens are introduced with crops and 

 sometimes become established. I once saw a large patch of teesdalia on a railway bank 

 near Ashford. The seeds had been tipped there in a load of pebble from Dungeness. 

 Examples of this sort are too numerous to mention here. The Forestry Commission are 

 conducting an experiment of great interest in that they surround their woodlands with 

 rabbit proof fences. One hopes, in the course of years, to see the revival of plants which 

 had been kept under by this tyrannous rodent. A simple and instructive designed experi- 

 ment at our disposal is the attempt to naturalise plants or insects. I once tried to intro- 

 duce Azolla into my pond. It was promptly eaten by the water snails. This plant is 

 common in ditches near Sarre. The water is slightly saline and possibly free of the water 

 snail on that account. The matter requires further investigation. Even a good guess 

 must be substantiated. 



It is time to bring these somewhat random remarks to a close. I remind you that 

 when you study the ecology of your neighbourhood you do not omit to pay attention to 

 the reverse side. The technique is simple, you draw up a list of "probables" before you 

 go out and tick them off" as you find them, those that are unmarked will remind you of 

 their absence by mute reproach from the page more particularly if some one else discovers 

 them later on. 



