DISTRIBUTION OF SPECIES 15 



way banks, of which I have given several examples in my 

 Island Life (p. 513, footnote). All these phenomena, and 

 many others which will be referred to later, are manifestly 

 due to that " struggle for existence " which is one of the great 

 factors of evolution through " survival of the fittest." 



A Lincolnshire clergyman (Rev. E. Adrian Woodruff e-Pea- 

 cock of Cadney) has long studied the distribution of plants in 

 a very minute and interesting manner, more especially in his 

 own parish, but very extensively over the whole county. His 

 more exact method is to divide up a field into squares of about 

 16 feet each way with pegs, and then to note on special forms 

 or note-books (1) a list of the species found in each square, 

 and (2) the frequency (or proportion) of the occurrence of 

 each species. From these the frequency over the whole field 

 can be estimated, and the botanical peculiarities of various 

 fields very accurately determined. By comparing the detailed 

 flora of each field with its surface-geology, aspect, altitude, 

 degree of moisture or aridity, etc., a very accurate conclusion 

 as to the likes and dislikes of particular plants may be arrived 

 at. 



As an example of the detailed treatment of a rather uncom- 

 mon yet widely distributed plant, he has sent me a copy of his 

 paper on the Black Horehound (Ballota nigra), sl species not 

 uncommon over much of Central Europe, but scattered over 

 Central and Southern Britain only in a few favourable locali- 

 ties. In Lincolnshire it is found all over the county in suitable 

 spots, but prefers a warm, open, and limy soil, as shown by 

 150 records giving notes of its occurrence. The general results 

 of the inquiry are thus given: 



"AVhen the sheets of notes are analysed the following points 

 come out. It is a hedge and ditch-side species, but it seems to 

 prefer a bank to the flat in the proportion of 10 to 1 ; the sunny 

 bank to the shady side of a road running east and west in nearly 

 the same proportion. On sandy soils it seems to get away from 

 the villages to a greater distance than on clays, but perhaps the 

 rabbit may explain this. It extends from Cadney village along 



